The frequency of an activity refers to the A. Length of time it takes for an exercise or group of exercises to be complete

B. classification of exercise

C. amount of energy exerted while performing and exercise

D. number of times an exercise or group of exercises is performed Within certain amount of time frame

The answer would be "D" Because the definition of frequency is the number of times you do something in a certain amount of time.

Explanation:

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the gravitational force on an object increase as the mass of an object also, im not going to report you, but this question should be under the science category, not health