The recommended amount of exercise for healthy adults between the ages of 18 and 65 years is:
A) moderate anaerobic activity for at least 30 minutes,three days each week.
B) intense anaerobic activity for at least 15 minutes,seven days each week.
C) moderate aerobic activity for at least 60 minutes,five days each week.
D) moderate aerobic activity for at least 30 minutes,five days each week.