Blood pressure decreases from arteries to veins

Steps:

• Recall blood pressure is highest in arteries from heart pumping.
• Note pressure drops sharply in capillaries due to friction in narrow vessels.
• Observe further gradual drop in veins as blood flows back to heart.
• Match values: arteries ~13 kPa, capillaries ~4 kPa, veins ~0.6 kPa.

Why D is correct:

• D (13.0, 4.0, 0.6) follows the physiological law of pressure gradient, decreasing from arteries to capillaries to veins per Poiseuille's law on resistance.

Why the others are wrong:

• A: Incorrect order with lowest in artery, violating high arterial pressure.
• B: Puts highest pressure in capillary, ignoring arterial peak.
• C: Assigns high pressure to vein, reversing the flow gradient.

Final answer: D