Identifying blood vessels by direction of blood flow

Steps:

• Determine P: carries oxygenated blood away from heart to body, defining it as an artery.
• Determine Q: carries deoxygenated blood toward heart from body, defining it as a vein.
• Determine R: carries deoxygenated blood away from heart to lungs, defining it as an artery (pulmonary artery).

Why A is correct:

• Arteries conduct blood away from the heart under high pressure, matching P and R; veins return blood to the heart, matching Q.

Why the others are wrong:

• B: R is an artery, not a capillary, as capillaries enable exchange, not transport from heart.
• C: P is an artery, not a vein; direction away from heart rules out vein.
• D: R is an artery, not a vein; it carries blood away from heart.

Final answer: A