【正确答案】 C

【答案解析】[解析] 23-25
M: Thank you for being on our show, Dr. Lin. Now I know many of us have trouble sleeping. Is this a very big problem?
W: Yes, it is. (23) Research suggests that while the amount of sleep people need varies, many people get an hour less than they need every night.
M: That's interesting. So, what do you suggest for people who have trouble sleeping?
W: Well, the first thing to remember is to be careful about what you eat and drink before you go to bed. (24) Most people know that you should avoid drinking coffee, but it's also best to avoid soda drinks because they also contain caffeine.
M: Is it a good idea to take naps during the day?
W: Not really. It's best to avoid napping if you can. It will make it harder to sleep at night because you won't be tired. It's also important to find a regular time to go to bed. Don't go to bed early one day and late the next. Your body needs to know when it's time to sleep.
M: Should you get up if you can't sleep?
W: Yes, if you can't sleep after 30 minutes, get up and do something until you feel sleepy. (25) One final thing, research suggests it's better to sleep on your back. It helps you relax and breathe more deeply. It's not good to lie on your stomach or your side.
M: Well, thanks again, Dr. Lin. I think I'm starting to feel sleepy already!
Q: What is the problem with sleeping?

[答案详解] 对话中提到研究发现尽管不同的人需要的睡眠时间不同，但很多人睡眠时间不够，故选C)项。