HMS, BM EQ-Bank 53 MC

During steady-state running, which statement correctly identifies how the structure of the respiratory and circulatory systems enables oxygen delivery to working leg muscles?

Thick-walled capillaries protect red blood cells in the muscles
Alveoli and surrounding capillaries maximise gas exchange
Pulmonary veins carry oxygen-rich blood to the right atrium
Bronchioles exchange oxygen directly with the blood

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\(B\)

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B is correct: Thin-walled alveoli surrounded by capillaries provide a large surface area and short diffusion distance for gas exchange.

Other Options:

A is incorrect: Capillary walls are only one cell thick, which allows diffusion.
C is incorrect: Pulmonary veins return oxygen-rich blood to the left atrium.
D is incorrect: Gas exchange occurs in the alveoli, not the bronchioles.