Transport in Humans: Blood, Heart, Blood Vessels, Coronary Heart Disease and Lymph

1. Which blood vessel normally carries blood with the lowest oxygen concentration?

A pulmonary vein
B aorta
C pulmonary artery
D coronary artery

2. Which row correctly compares arteries and veins?

A arteries have valves; veins have thick muscular walls
B arteries carry blood at high pressure; veins have a wider lumen
C arteries always carry oxygenated blood; veins always carry deoxygenated blood
D arteries carry blood to the heart; veins carry blood away from the heart

3. Which feature of a red blood cell directly increases the amount of oxygen it can carry?

A presence of a nucleus
B biconcave shape only
C absence of nucleus giving more space for haemoglobin
D thick cell wall preventing bursting

4. Which component of blood is mainly responsible for transporting urea, hormones and carbon dioxide in solution?

A red blood cells
B white blood cells
C plasma
D platelets

5. Which statement about platelets is correct?

A they contain haemoglobin and transport oxygen
B they produce antibodies against pathogens
C they are cell fragments involved in blood clotting
D they engulf bacteria by phagocytosis

6. Which sequence correctly shows the path of blood through the heart and lungs?

A right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium
B left atrium → left ventricle → pulmonary artery → lungs → pulmonary vein → right atrium
C right ventricle → right atrium → pulmonary vein → lungs → pulmonary artery → left ventricle
D left ventricle → left atrium → vena cava → lungs → aorta → right atrium

7. Why is the wall of the left ventricle thicker than the wall of the right ventricle?

A it pumps blood to the lungs only
B it pumps blood at higher pressure to the whole body
C it receives blood directly from the vena cava
D it prevents oxygenated blood from entering the aorta

8. Which blood vessel supplies oxygen and glucose to the heart muscle itself?

A pulmonary artery
B coronary artery
C vena cava
D pulmonary vein

9. Which condition most directly results from the narrowing or blockage of coronary arteries?

A emphysema
B coronary heart disease
C anaemia
D diabetes

10. Which combination increases the risk of coronary heart disease most directly?

A high fibre diet and regular exercise
B high saturated fat diet, smoking and high blood pressure
C low salt intake and low blood cholesterol
D high vitamin C intake and low blood glucose

11. A person has a stroke volume of 70 cm³ and a heart rate of 80 beats per minute.
    What is the cardiac output?

A 150 cm³/min
B 560 cm³/min
C 5600 cm³/min
D 56 000 cm³/min

12. Which blood vessel has the highest blood pressure during normal circulation?

A vena cava
B pulmonary vein
C aorta
D capillary

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

13. What is the main function of valves in veins?

A to increase blood pressure by contraction
B to prevent backflow of blood
C to exchange materials with tissues
D to produce red blood cells

14. Which row correctly identifies the blood entering and leaving the right side of the heart?

A enters from pulmonary vein; leaves through aorta
B enters from vena cava; leaves through pulmonary artery
C enters from aorta; leaves through pulmonary vein
D enters from pulmonary artery; leaves through vena cava

15. Which vessel carries oxygenated blood from the lungs to the heart?

A pulmonary artery
B pulmonary vein
C aorta
D vena cava

16. Which statement about the pulmonary artery is correct?

A it carries oxygenated blood from the lungs to the heart
B it carries deoxygenated blood from the heart to the lungs
C it carries oxygenated blood from the heart to the body
D it carries deoxygenated blood from the body to the heart

17. Which feature makes capillaries suitable for exchange of materials?

A thick muscular walls and narrow lumen
B walls one cell thick and close contact with tissues
C valves and low pressure
D waterproof walls and no pores

18. At the arteriole end of a capillary bed, tissue fluid is formed mainly because

A oxygen actively transports water out of red blood cells
B blood pressure forces plasma out through capillary walls
C platelets dissolve the capillary wall
D lymph flows backwards into blood capillaries

19. Which substances are least likely to leave the blood capillary to form tissue fluid?

A oxygen and glucose
B water and mineral ions
C plasma proteins and red blood cells
D amino acids and carbon dioxide

20. Which statement correctly describes lymph?

A lymph is blood without plasma
B lymph is tissue fluid that has entered lymph vessels
C lymph is oxygenated blood in arteries
D lymph is bile transported from the liver

21. Which feature helps lymph move in one direction through lymph vessels?

A thick elastic arteries
B valves and muscle contractions
C haemoglobin and platelets
D high pressure from the left ventricle

22. Which function is carried out by lymph nodes?

A pumping blood to the lungs
B filtering pathogens and containing lymphocytes
C producing bile for fat digestion
D absorbing oxygen from alveoli

23. A person has a cardiac output of 4.8 dm³/min and a heart rate of 60 beats/min.
    What is the stroke volume?

A 8 cm³
B 80 cm³
C 800 cm³
D 288 cm³

24. Which situation is most likely to cause tissue swelling due to poor drainage of tissue fluid?

A increased haemoglobin in red blood cells
B blockage of lymph vessels
C faster clotting by platelets
D increased oxygen concentration in arteries

25. Which row correctly matches blood component and function?

A red blood cell: produces antibodies
B platelet: transports oxygen
C white blood cell: defence against pathogens
D plasma: forms fibrin threads directly

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

26. Which valve is found between the left atrium and left ventricle?

A tricuspid valve
B bicuspid valve
C pulmonary semilunar valve
D aortic semilunar valve

27. What happens when the ventricles contract?

A atrioventricular valves open and semilunar valves close
B atrioventricular valves close and semilunar valves open
C all valves close and no blood leaves the heart
D all valves open and blood flows in all directions

28. Why is the circulatory system in humans described as double circulation?

A blood passes through the heart twice in one complete circuit of the body
B blood contains both red and white blood cells
C arteries and veins always carry oxygenated blood
D blood flows in two directions inside every vessel

29. Which pathway correctly shows blood flow from the body tissues back to the body tissues?

A body → vena cava → right heart → lungs → left heart → aorta → body
B body → aorta → right heart → lungs → left heart → vena cava → body
C body → pulmonary vein → right heart → lungs → left heart → pulmonary artery → body
D body → vena cava → left heart → lungs → right heart → aorta → body

30. Which change would most likely increase oxygen transport capacity in a healthy person over time?

A fewer red blood cells
B lower haemoglobin concentration
C increased red blood cell production
D reduced plasma volume only

31. Which statement about haemoglobin is correct?

A it carries oxygen mainly in plasma
B it combines reversibly with oxygen
C it is found mainly in platelets
D it digests pathogens in lymph nodes

32. Which blood component is most directly involved in phagocytosis?

A red blood cell
B platelet
C phagocyte white blood cell
D plasma protein only

33. Which statement correctly compares phagocytes and lymphocytes?

A phagocytes produce haemoglobin; lymphocytes transport oxygen
B phagocytes engulf pathogens; lymphocytes produce antibodies
C phagocytes form fibrin; lymphocytes form platelets
D phagocytes transport urea; lymphocytes transport glucose

34. A cut blood vessel begins to clot.
    Which sequence is most accurate?

A platelets release chemicals → fibrin forms → blood cells trapped → clot forms
B red blood cells release bile → glucose forms → clot dissolves
C plasma proteins become haemoglobin → artery relaxes → clot forms
D lymphocytes become platelets → capillary bursts → clot forms

35. Which statement about arteries is correct?

A they have thin walls and many valves
B they carry blood at low pressure
C they have thick muscular elastic walls
D they allow exchange through one-cell-thick walls

36. Which statement about veins is correct?

A they have thick walls and no lumen
B they carry blood under lower pressure than arteries
C they carry blood away from the heart
D they have walls one cell thick

37. Which statement about capillaries is correct?

A they connect arteries directly to veins without arterioles or venules
B they have one-cell-thick walls for exchange
C they contain valves to prevent backflow
D they carry blood at the highest pressure in the body

38. Which change would most likely occur during exercise?

A heart rate decreases and cardiac output decreases
B heart rate increases and blood flow to muscles increases
C oxygen demand in muscles decreases
D carbon dioxide production in muscles stops

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

39. A person’s heart rate increases from 70 to 110 beats per minute, while stroke volume increases from 70 cm³ to 100 cm³.
    What happens to cardiac output?

A increases from 4.9 dm³/min to 11.0 dm³/min
B increases from 49 dm³/min to 110 dm³/min
C decreases from 11.0 dm³/min to 4.9 dm³/min
D remains constant because stroke volume cancels heart rate

40. Which statement best explains why arteries do not usually need valves along their length?

A blood in arteries is under high pressure from the heart
B arteries carry only deoxygenated blood
C artery walls are one cell thick
D arteries contain lymph nodes

41. Which part of the heart receives blood from the pulmonary veins?

A right atrium
B right ventricle
C left atrium
D left ventricle

42. Which part of the heart pumps blood into the aorta?

A right atrium
B right ventricle
C left atrium
D left ventricle

43. Which statement correctly describes coronary thrombosis?

A a clot blocks a coronary artery and reduces blood supply to heart muscle
B a valve between atrium and ventricle becomes wider
C a lymph vessel carries too much oxygen to the heart
D the pulmonary vein becomes filled with bile

44. Which event is most likely to cause a heart attack?

A increased oxygen delivery to cardiac muscle
B blockage of a coronary artery by a clot
C faster lymph drainage from heart tissue
D more elastic walls in coronary arteries

45. Which treatment helps keep a narrowed coronary artery open?

A dialysis
B stent
C vaccination
D ventilator

46. Which treatment uses a blood vessel from another part of the body to create an alternative route around a blocked coronary artery?

A coronary bypass surgery
B antibiotic treatment
C blood transfusion only
D lymph node removal

47. Which lifestyle change would reduce the risk of coronary heart disease?

A increasing smoking to reduce stress
B increasing saturated fat intake
C regular aerobic exercise and reducing saturated fat intake
D avoiding all fibre and increasing salt intake

48. Which statement about atherosclerosis is correct?

A fatty deposits build up in artery walls and narrow the lumen
B red blood cells digest artery walls and widen the lumen
C lymph nodes block veins and stop clotting
D plasma proteins remove all cholesterol from arteries

49. Which blood vessel would contain blood with the highest glucose concentration shortly after absorption from the small intestine?

A hepatic portal vein
B pulmonary artery
C vena cava
D coronary vein

50. Which statement is correct?

A arteries always carry oxygenated blood and veins always carry deoxygenated blood
B pulmonary artery and pulmonary vein are exceptions to the usual oxygenation pattern
C capillaries have the thickest walls because pressure is highest there
D lymph vessels pump blood directly from the left ventricle to the body

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

1. Answer: C
   A is wrong because pulmonary vein carries oxygenated blood from lungs to heart.
   B is wrong because the aorta carries oxygenated blood from the left ventricle to the body.
   C is correct because the pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.
   D is wrong because coronary arteries supply oxygenated blood to the heart muscle.

2. Answer: B
   A is wrong because veins have valves, while arteries have thick muscular elastic walls.
   B is correct because arteries carry blood at high pressure and veins usually have wider lumens.
   C is wrong because pulmonary artery and pulmonary vein are exceptions.
   D is wrong because arteries carry blood away from the heart; veins carry blood towards the heart.

3. Answer: C
   A is wrong because mature red blood cells do not have a nucleus.
   B is incomplete because biconcave shape increases surface area, but does not directly increase haemoglobin space as strongly as nucleus loss.
   C is correct because absence of nucleus gives more space for haemoglobin, allowing more oxygen transport.
   D is wrong because red blood cells have no cell wall.

4. Answer: C
   A is wrong because red blood cells mainly transport oxygen.
   B is wrong because white blood cells are mainly involved in defence.
   C is correct because plasma transports dissolved substances such as urea, hormones and some carbon dioxide.
   D is wrong because platelets are involved in blood clotting.

5. Answer: C
   A is wrong because red blood cells contain haemoglobin.
   B is wrong because lymphocytes produce antibodies.
   C is correct because platelets are cell fragments involved in blood clotting.
   D is wrong because phagocytes engulf bacteria.

6. Answer: A
   A is correct because deoxygenated blood moves from right atrium → right ventricle → pulmonary artery → lungs, then oxygenated blood returns by pulmonary vein to left atrium.
   B is wrong because the left side pumps blood to the body, not through the pulmonary artery.
   C is wrong because blood does not flow from right ventricle back to right atrium in normal circulation.
   D is wrong because it mixes up left/right heart and major vessels.

7. Answer: B
   A is wrong because the right ventricle pumps blood to the lungs.
   B is correct because the left ventricle pumps blood to the whole body at high pressure.
   C is wrong because the right atrium receives blood from the vena cava.
   D is wrong because the left ventricle pumps oxygenated blood into the aorta.

8. Answer: B
   A is wrong because the pulmonary artery carries blood to the lungs.
   B is correct because coronary arteries supply oxygen and glucose to the heart muscle.
   C is wrong because the vena cava returns deoxygenated blood to the heart.
   D is wrong because the pulmonary vein returns oxygenated blood from lungs to heart.

9. Answer: B
   A is wrong because emphysema is a lung disease.
   B is correct because narrowing/blockage of coronary arteries causes coronary heart disease.
   C is wrong because anaemia is linked to low haemoglobin/red blood cells.
   D is wrong because diabetes involves blood glucose control.

10. Answer: B
    A is wrong because high fibre and regular exercise reduce risk.
    B is correct because saturated fat, smoking and high blood pressure increase coronary heart disease risk.
    C is wrong because low salt and low blood cholesterol reduce risk.
    D is wrong because vitamin C and low blood glucose are not the major direct CHD risk combination.

11. Answer: C
    Cardiac output = stroke volume × heart rate = 70 cm³ × 80 = 5600 cm³/min.
    A is wrong because it adds incorrectly.
    B is too small by a factor of 10.
    C is correct.
    D is too large by a factor of 10.

12. Answer: C
    A is wrong because vena cava has low pressure.
    B is wrong because pulmonary vein pressure is lower than aorta.
    C is correct because the aorta receives blood directly from the left ventricle at high pressure.
    D is wrong because capillary pressure is lower than arterial pressure.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

13. Answer: B
    A is wrong because veins do not increase pressure by contraction like the heart.
    B is correct because valves prevent backflow of blood in veins.
    C is wrong because exchange mainly occurs in capillaries.
    D is wrong because red blood cells are produced in bone marrow.

14. Answer: B
    A is wrong because pulmonary veins enter the left atrium, not the right side.
    B is correct because the right side receives blood from the vena cava and sends it through the pulmonary artery.
    C is wrong because the aorta leaves the left ventricle.
    D is wrong because pulmonary artery carries blood away from the right ventricle.

15. Answer: B
    A is wrong because pulmonary artery carries deoxygenated blood to the lungs.
    B is correct because pulmonary veins carry oxygenated blood from lungs to the left atrium.
    C is wrong because the aorta carries oxygenated blood from heart to body.
    D is wrong because vena cava carries deoxygenated blood to the heart.

16. Answer: B
    A is wrong because that describes the pulmonary vein.
    B is correct because the pulmonary artery carries deoxygenated blood from the heart to the lungs.
    C is wrong because that describes the aorta.
    D is wrong because that describes the vena cava.

17. Answer: B
    A is wrong because thick muscular walls are features of arteries, not capillaries.
    B is correct because capillaries have one-cell-thick walls and lie close to tissues, giving a short diffusion distance.
    C is wrong because valves are found in veins/lymph vessels, not capillaries.
    D is wrong because capillary walls are permeable enough for exchange.

18. Answer: B
    A is wrong because oxygen does not actively transport water out of red blood cells.
    B is correct because blood pressure forces plasma out of capillaries to form tissue fluid.
    C is wrong because platelets do not dissolve capillary walls.
    D is wrong because lymph drains tissue fluid away; it does not normally flow backwards into capillaries.

19. Answer: C
    A is wrong because oxygen and glucose can leave capillaries to supply cells.
    B is wrong because water and mineral ions can leave to form tissue fluid.
    C is correct because red blood cells and large plasma proteins usually remain inside capillaries.
    D is wrong because amino acids can leave and carbon dioxide can enter/leave depending on gradient.

20. Answer: B
    A is wrong because lymph is not blood without plasma.
    B is correct because lymph is tissue fluid that has entered lymph vessels.
    C is wrong because oxygenated blood in arteries is not lymph.
    D is wrong because bile is part of digestion, not lymph.

21. Answer: B
    A is wrong because lymph does not move through arteries.
    B is correct because valves and muscle contractions help lymph move one way.
    C is wrong because haemoglobin and platelets are blood components, not the main lymph-moving mechanism.
    D is wrong because lymph is not pumped directly by the left ventricle.

22. Answer: B
    A is wrong because the heart pumps blood to lungs.
    B is correct because lymph nodes filter pathogens and contain lymphocytes.
    C is wrong because the liver produces bile.
    D is wrong because alveoli are for gas exchange.

23. Answer: B
    Cardiac output = 4.8 dm³/min = 4800 cm³/min.
    Stroke volume = cardiac output ÷ heart rate = 4800 ÷ 60 = 80 cm³.
    A is too small.
    B is correct.
    C is too large.
    D incorrectly multiplies/divides values.

24. Answer: B
    A is wrong because more haemoglobin does not cause tissue fluid drainage failure.
    B is correct because blocked lymph vessels prevent tissue fluid from draining, causing swelling.
    C is wrong because faster clotting does not directly cause tissue fluid accumulation.
    D is wrong because oxygen concentration in arteries is not the main cause of swelling.

25. Answer: C
    A is wrong because lymphocytes produce antibodies, not red blood cells.
    B is wrong because red blood cells transport oxygen, not platelets.
    C is correct because white blood cells defend against pathogens.
    D is wrong because fibrin formation involves plasma protein fibrinogen and clotting factors, but “plasma forms fibrin threads directly” is too inaccurate for the component-function match.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

26. Answer: B
    A is wrong because the tricuspid valve is between right atrium and right ventricle.
    B is correct because the bicuspid/mitral valve is between left atrium and left ventricle.
    C is wrong because the pulmonary semilunar valve is between right ventricle and pulmonary artery.
    D is wrong because the aortic semilunar valve is between left ventricle and aorta.

27. Answer: B
    A is wrong because atrioventricular valves close during ventricular contraction.
    B is correct because ventricles contracting close the atrioventricular valves and open the semilunar valves.
    C is wrong because blood does leave the heart during ventricular contraction.
    D is wrong because valves do not all open; that would cause backflow chaos, plumbing nightmare.

28. Answer: A
    A is correct because blood passes through the heart twice in one complete circuit: once to lungs and once to body.
    B is wrong because red and white cells do not define double circulation.
    C is wrong because arteries and veins do not always follow oxygenation rules.
    D is wrong because blood does not flow in two directions inside every vessel.

29. Answer: A
    A is correct because blood travels body → vena cava → right heart → lungs → left heart → aorta → body.
    B is wrong because the aorta carries blood away from the left heart, not back from body to right heart.
    C is wrong because pulmonary vessels are placed incorrectly.
    D is wrong because vena cava enters the right heart, not left heart.

30. Answer: C
    A is wrong because fewer red blood cells reduce oxygen transport.
    B is wrong because lower haemoglobin reduces oxygen carrying capacity.
    C is correct because more red blood cells increase oxygen transport capacity.
    D is wrong because reduced plasma volume alone does not directly increase oxygen-carrying capacity safely.

31. Answer: B
    A is wrong because oxygen is mainly carried by haemoglobin inside red blood cells, not plasma.
    B is correct because haemoglobin combines reversibly with oxygen to form oxyhaemoglobin.
    C is wrong because haemoglobin is in red blood cells, not platelets.
    D is wrong because haemoglobin does not digest pathogens.

32. Answer: C
    A is wrong because red blood cells transport oxygen.
    B is wrong because platelets clot blood.
    C is correct because phagocyte white blood cells engulf pathogens.
    D is wrong because plasma proteins alone do not carry out phagocytosis.

33. Answer: B
    A is wrong because red blood cells transport oxygen using haemoglobin.
    B is correct because phagocytes engulf pathogens and lymphocytes produce antibodies.
    C is wrong because platelets and fibrin are involved in clotting.
    D is wrong because plasma transports urea and glucose.

34. Answer: A
    A is correct because platelets trigger clotting, fibrin threads form, blood cells are trapped and a clot forms.
    B is wrong because red blood cells do not release bile.
    C is wrong because plasma proteins do not become haemoglobin.
    D is wrong because lymphocytes do not become platelets.

35. Answer: C
    A is wrong because arteries usually do not have many valves along their length.
    B is wrong because arteries carry blood at high pressure.
    C is correct because arteries have thick muscular elastic walls to withstand and maintain pressure.
    D is wrong because one-cell-thick walls are capillary features.

36. Answer: B
    A is wrong because veins have thinner walls and a wider lumen.
    B is correct because veins carry blood under lower pressure than arteries.
    C is wrong because veins carry blood towards the heart.
    D is wrong because one-cell-thick walls describe capillaries.

37. Answer: B
    A is wrong because arteries branch into arterioles, then capillaries, then venules and veins.
    B is correct because capillaries have one-cell-thick walls for exchange.
    C is wrong because valves are not a capillary feature.
    D is wrong because pressure is highest in arteries, especially the aorta.

38. Answer: B
    A is wrong because during exercise heart rate and cardiac output increase.
    B is correct because muscles need more oxygen and glucose, so heart rate and blood flow to muscles increase.
    C is wrong because oxygen demand increases.
    D is wrong because carbon dioxide production increases, not stops.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.

39. Answer: A
    Initial cardiac output = 70 × 70 = 4900 cm³/min = 4.9 dm³/min.
    Final cardiac output = 110 × 100 = 11 000 cm³/min = 11.0 dm³/min.
    A is correct.
    B is wrong because it does not convert cm³ to dm³ properly.
    C is wrong because cardiac output increases, not decreases.
    D is wrong because stroke volume and heart rate multiply; they do not cancel.

40. Answer: A
    A is correct because arterial blood is under high pressure from the heart, so backflow is less likely.
    B is wrong because arteries do not carry only deoxygenated blood.
    C is wrong because capillaries, not arteries, have one-cell-thick walls.
    D is wrong because arteries do not contain lymph nodes.

41. Answer: C
    A is wrong because the right atrium receives blood from the vena cava.
    B is wrong because the right ventricle receives blood from the right atrium.
    C is correct because pulmonary veins carry oxygenated blood into the left atrium.
    D is wrong because the left ventricle receives blood from the left atrium.

42. Answer: D
    A is wrong because the right atrium receives blood from the vena cava.
    B is wrong because the right ventricle pumps blood into the pulmonary artery.
    C is wrong because the left atrium receives blood from pulmonary veins.
    D is correct because the left ventricle pumps blood into the aorta.

43. Answer: A
    A is correct because coronary thrombosis is a clot blocking a coronary artery, reducing blood supply to heart muscle.
    B is wrong because valve widening is not coronary thrombosis.
    C is wrong because lymph vessels do not carry oxygen-rich blood to the heart muscle.
    D is wrong because the pulmonary vein does not fill with bile.

44. Answer: B
    A is wrong because increased oxygen delivery would reduce risk of heart muscle damage.
    B is correct because blockage of a coronary artery by a clot can cut off oxygen to heart muscle, causing a heart attack.
    C is wrong because faster lymph drainage does not cause a heart attack.
    D is wrong because more elastic coronary arteries would generally help blood flow.

45. Answer: B
    A is wrong because dialysis treats kidney failure.
    B is correct because a stent helps keep a narrowed coronary artery open.
    C is wrong because vaccination prevents infectious disease, not narrowed arteries.
    D is wrong because a ventilator assists breathing.

46. Answer: A
    A is correct because coronary bypass surgery uses a blood vessel graft to route blood around a blocked coronary artery.
    B is wrong because antibiotics treat bacterial infections.
    C is wrong because blood transfusion does not create an alternative coronary route.
    D is wrong because lymph node removal does not bypass coronary arteries.

47. Answer: C
    A is wrong because smoking increases CHD risk.
    B is wrong because saturated fat increases blood cholesterol and CHD risk.
    C is correct because regular aerobic exercise and reducing saturated fat intake reduce CHD risk.
    D is wrong because low fibre and high salt are unhealthy risk factors.

48. Answer: A
    A is correct because atherosclerosis involves fatty deposits building up in artery walls, narrowing the lumen.
    B is wrong because red blood cells do not digest artery walls.
    C is wrong because lymph nodes do not block veins in atherosclerosis.
    D is wrong because plasma proteins do not remove all cholesterol from arteries.

49. Answer: A
    A is correct because the hepatic portal vein carries blood rich in absorbed glucose from the small intestine to the liver.
    B is wrong because the pulmonary artery carries deoxygenated blood to lungs.
    C is wrong because the vena cava carries blood returning from the body after mixing.
    D is wrong because the coronary vein drains blood from heart muscle.

50. Answer: B
    A is wrong because pulmonary artery and pulmonary vein are exceptions.
    B is correct because the pulmonary artery carries deoxygenated blood and pulmonary vein carries oxygenated blood, opposite to the usual artery/vein oxygen pattern.
    C is wrong because capillaries have the thinnest walls, not thickest.
    D is wrong because lymph vessels carry lymph, not blood pumped by the left ventricle.

Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 11 World Records and 7 Distinctions, Educate A Change.