Which of the following is true of physical activity?

A. Involuntary physiological functions such as respiration and beating of the heart are part of physical activity.
B. Body size affects energy expended for physical activity.
C. Physical activity accounts for 50–70 percent of total energy expenditure.
D. The amount of energy associated with physical activity depends on the amount of food consumed.

B) Body size affects energy expended for physical activity.

Explanation: Physical activity can be defined as any movement of the body produced by skeletal muscles that uses energy. Lack of physical activity is associated with negative health outcomes while increased physical activity can improve physical as well as mental health.

Physical activities requires the use of energy and at such, body size affects the energy expended for physical activity.

the answer is nerve impulses.

good