A、It may become a habit. B、It works very well. C、It is a harmless method. D、It is too expensive. A题目问的是关于喝咖啡提神，说话者是如何觉得的。由定位句可知，

When you’ re feeling weak and tired, the worst thing to do is to take a nap. It won’t restore your stamina. On the contrary, what happens then is your body loses even more energy than it had before, making you even more lethargic.
    You may also have these poor habits that worsen the problems. Do you stay in the same small area without getting up to move around? Does your job require that you sit down the whole day in front of a computer? Any or all of these reasons might be the cause of your energy loss, keeping your energy level low.
    What should you do, then, at those moments when you feel so tired even though you’ve got enough sleep? A cup of coffee won’ t help much either, as it is easy to get addicted to the caffeine. The best and most natural thing to do is to take a brisk walk.
    Q19: According to the broadcast, what happens when you take a nap when you’ re feeling tired?
    Q20: What is one of the causes of having a low energy level?
    Q21: How does the speaker feel about drinking coffee to increase one’ s energy?