Physical activity is an inclusive term that refers to any expenditure of energy brought about by bodily movement via the skeletal muscles; as such, it includes the complete spectrum of activity from very low resting levels to maximal exertion. exercise is a component of physical activity. the distinguishing characteristic of exercise is that it is a structured activity specifically planned to develop and maintain physical fitness.

"exercise." britannica school. encyclopaedia britannica, inc., 2013. web. 21 oct. 2013.

how is the word expenditure used in this excerpt?
a. to show the type of activities completed by skeletal muscles

b. to identify how much energy is used at low resting levels

c. to describe the amount of movement required for maximal exertion

d. to highlight that a physical activity requires a body to use energy