A、He lacks time. B、He lacks willpower. C、He lacks sleep. D、He lacks medicine. B

A: Hello, Doctor Martin.
B: Hello, it’s you again, Tom. What’s wrong with you this time? Anything I can do for you?
A: Oh, yes. Doctor, I need some medicine. You see, I often feel tired and don’t feel like doing anything.
B: Let me see ... m, I think nothing is wrong with you, Tom. Your problem is just you are overweight. I told you to exercise every day. Did you do that?
A: Well, you see, doctor, I always get up too late in the morning. I have no time to do morning exercises.
B: Then do you exercise in the afternoon? At least an hour a day?
A: Well, I ... I have to work on the reading assignment. Oh, piles of books to finish every day.
B: Then what about the evening? Many people squeeze in time to exercise in the evening, If you can do that, you’ll soon lose weight. And things will be better.
A: But Doctor, I love to watch TV in the evening.
B: Well, Tom, my advice to you is to limit TV-watching to only once or twice in a week, and jog for an hour every day.
A: But Doctor ...
B: No buts, Tom. This is totally a willpower problem. You must follow my advice, or you’ll soon become too heavy to move any more.
A: Thanks anyway ... Doctor ... should I come to see you next week?
B: I don’t think so. Exercise more and eat low-fat food. That’s the best medicine for you.