Blood Flow in Capillary Networks

Steps:

• Arteries branch into smaller vessels that carry blood away from the heart to tissues.
• These smaller vessels form capillary networks, where P receives blood directly from arteries.
• Capillaries then deliver blood to veins via Q, completing the exchange network.
• Thus, P transports blood originating from arteries, while Q directs it toward veins.

Why C is correct:

• In the circulatory system, capillaries connect arteries to veins, so P carries deoxygenated blood from arteries for nutrient exchange, and Q carries it into veins for return to the heart (definition of capillary function).

Why the others are wrong:

• A: Reverses flow; no vessels carry blood into arteries except the aorta from the heart.
• B: Misplaces venous return; veins carry to the heart, not from veins to arteries.
• D: Ignores arterial input; both cannot originate from veins in a systemic network.

Final answer: C