Your body has its own biological clock, and when you continuously work against it, you're

Relax before you try to fall asleep. Whether you use Transcendental Meditation, deep breathing, or some other systems, it is important to slow down before bedtime.

Try stimulus control. Psychologist Richard Bootzin has developed this program of "stimulus control to disassociate cues for sleep from those for other activities."

—Do not use your bed for any activity other than sleep, such as reading, writing letters, watching TV.

—If you are in bed for more than ten minutes without falling asleep, go to another room. Return to bed when you're ready to try again.

—Set your alarm clock for the same time every morning. Arise when it rings, no matter how much or how little. sleep you've had.

—Do not nap during the day. (Some researchers approve of naps, but Bootzin says they're not for insomniacs.)

Try exercise as a soporific. Do your exercise at least two hours before retiring, preferably earlier. Exercise may be stimulating if done too late.

Avoid caffeine. Caffeine is a common disrupter of sleep, even when not the primary cause of insomnia. Soft drinks and chocolate contain caffeine, so large quantities should be avoided at bedtime. The stimulating action of caffeine usually reaches a peak two to four hours after it is ingested. But caffeine taken up to seven hours before bed can disrupt sleep.

Be careful about alcohol. A drink before bed may actually help you sleep better in the early hours of the night, but may cause restlessness later.

Arrange the proper environment. The rapidity with which some people fall asleep depends on environmental factors, like a comfortable bed, right noise and light levels, correct temperature. If any item is in disarray, the onset of sleep can be delayed for hours. When your environment totally changes, as in a hotel room, it's common to react with disturbed sleep. Usually by the second night, almost always by the third, the body adapts.

Try some of the sleep gadgets. You can purchase pollen—free pillows for allergy sufferers, bed vibrators, a "white noise" machine guaranteed to drown out other sounds, long-playing sleep records, a bed that rocks, a sound proof bed surrounded by four plastic walls, a bed that will catapult you to the floor at wake-up time.

Eat your way to sleep. Some foods contain an amino acid called L-tryptophan which doctors believe can help in duce sleep.

If all this fails, why not count sheep？ According to Harvard psychologists Richard Davidson and Gary Schwarts, the images of sheep prevent your mind form. focusing on anxiety-provoking events that might otherwise keep you awake.

Before going to bed, you'd better ______.

A．breathe deeply

B．have a biological clock

C．invite problems

D．relax