根据以下材料，回答36-39题
Sound sleep occurs when one's internalclock is regulated. Circadian rhythms (生理节奏) can becomecompromised quite easily. Many people with sleep troubles tend to varybedtimes. To avoid this common problem, sleep sufferers should go to bed andwake up at the same time every day. To help improve circadian rhythms,sufferers should enjoy 15 minutes of sun exposure the first thing in themorning.
A bedtime routine can help preventinsomnia(失眠). One hour before bedtime, one should lower the lights and relax.Reading a book or listening to calm music can help prepare the body for a goodnight's sleep. Taking a warm, candlelit bath or drinking a cup of warm milk canalso help you prepare for deep sleep at night.
Stress can have a bad effect on the bodyand the ability to sleep. A daily exercise routine can help lower the body'sstress naturally. One can also manage stress by writing diaries. Writingdiaries can help people express their anxieties, plan for the future andimprove sleep. Other ways to lower stress include deep breathing exercises andprogressive muscle relaxation.
The light sending out fromcomputers, cellphones, tablets and televisions can cause sleep problems.Therefore, these items should be turned off at least an hour before bedtime.Additionally,lowering the backlight on these electronic devices earlier in theevening can help you fall asleep faster and stay asleep longer once bedtimearrives.
A perfect bedroom invites sweetsleep. Most people sleep better ina cool, dark, and quiet room. Lower the temperature in the room to 16 -20degrees for a peaceful night's sleep. A dark room can be accomplished byinstalling light blocking curtains or wearing a sleep mask. Noise can be reduced with eitherearplugs or a white noise machine. Finally, a comfortable mattress(床垫) and pillowsare essential to a good night's sleep.
What is the perfect condition forsleep
文章最后一段提到一个完美的卧室有助于甜蜜入睡，大多数人在凉爽、黑暗、安静的卧室能够睡得更好。房间里可以安装遮光窗帘，戴眼罩、耳塞或白色噪音机能够降低噪音。舒适的床垫和枕头也是高质量的睡眠所不可或缺的条件。因此选C。
