Strength training and stretching exercises should be done:
a. every day.
b. once each month.
c. two to three days a week.
d. once each week.

The answer is c. two to three days a week.  Strength exercises should be done two or three days a week to give the body time to heal after a strenuous workout.  Stretching is also important to prevent injury and to keep the muscles flexible.

the answer is nerve impulses.

good