The correct answer would be D, It depends upon the woman's level of activity.
Normally 20 to 30 minutes on daily exercise is enough for people to stay healthy and fit. But it is totally dependent upon the level of physical activity a person is doing. If a person's lifestyle is sedentary, which means he is not doing enough physical activities, then he should increase the time to exercise. Similarly if a person's lifestyle include more physical activity like standing job, then 20 to 30 mins exercise is more than enough for him to stay fit.
