The answer is letter D.
The best time to exercise differs for each individual. Some people are more active in the mornings than in the afternoons because the body is well rested from the good night's sleep. Others find it more energizing to work out in the later afternoon after all the tasks for the day has been accomplished because they seem to find that exercise reduces stress. Others choose different parts of the day for their workout to fit their schedules. There is actually no known best time to work-out, what matters is individuals find the time to engage in physical activity to maintain a healthy lifestyle.