George is running a 5-km race and his cells need more oxygen. which change will his body meet the increased demand for oxygen? a. his heart beating more quickly. b. his pancreas releasing more insulin. c. his breathing becoming more shallow. d. his sweat glands becoming more active.

A. His heart beating more quickly.

Explanation:

The physical activity like running increase the rate of heart beat and blood circulation in the body due to muscular activity. During running the body experiences the depletion of oxygen. Oxygen becomes the main requirement for cellular respiration during running. To meet the requirement of oxygen the heart pumps the blood faster so that the requirement in each cell get fulfilled through rapid blood circulation.

On the basis of the above explanation, A. His heart beating more quickly. is the correct option.

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