【正确答案】 C

【答案解析】[听力原文]
Do you have trouble sleeping at night? Then maybe this is for you. When you worry about needing sleep and twisting around, trying to find a comfortable position, you're probably only making matters worse. What happens is that your heart rate actually increases, making it more difficult to relax. You may also have some bad habits that contribute to the problem. Do you rest frequently during the day? Do you get virtually no exercise, or do you exercise strenuously late in the day? Do you often sleep a lot or sleep late on weekends? Any or all of these factors might be leading to your insomnia by disrupting your body's natural rhythm.
Insomnia is the inability to fall asleep or sleep restfully. It is a problem to nearly everyone at some time. A person may be awake for an hour in the middle of the night and then, next morning, feel that he hardly slept all night. Normally, worry about not getting enough sleep is the worst aspect of most insomnia. While what should you do then on those sleepless nights? Don't bother with sleeping pills. If necessary, take only the dosage prescribed by the doctors; any more can actually cause worse insomnia later. If insomnia is recurrent, however, it is important to find its possible causes and try to correct them.
The best thing to do is to drink milk or eat cheese or tuna fish. They are all rich in the amino acid that helps produce in the brain a neural transmitter that induces sleep. This neural transmitter will help you relax, and you'll be on the way to get a good night's sleep. Until tomorrow's broadcast, this has been another in the series "Hints for good health" by Doctor Goldson.

According to the speaker, what happens when you turn and twist to get comfortable?