Passage OneSound sleep occurs when one's internal clock is regul

Passage One
Sound sleep occurs when one's internal clock is regulated. Circadian rhythms（生理节奏）can become compromised quite easily. Many people with sleep troubles tend to vary bedtimes. To avoid this common problem, sleep sufferers should go to bed and wake up at the same time every day. to help improve circadian rhythms, sufferers should enjoy 15 minutes of sun exposure the first thing in the morning.
A bedtime routine can help prevent insomnia（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 good night's sleep. Taking a warm, candlelit bath or drinking a cup of warm milk can also help you prepare for deep sleep at night.
Stress can have a bad effect on the body and the ability to sleep. A daily exercise routine can help lower the body's stress naturally. One can also manage stress by writing diaries. Writing diaries can help people express their anxieties, plan for the future and improve sleep. Other ways to lower stress include deep breathing exercises and progressive muscle relaxation.
The light sending out from computers, 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 the evening can help you fall asleep faster and stay asleep longer once bedtime arrives.
A perfect bedroom invites sweet sleep. Most people sleep better in a cool, dark, and quiet room. Lower the temperature in the room to 16~20 degrees for a peaceful night's sleep. A dark room can be accomplished by installing light blocking curtains or wearing a sleep mask. Noise can be reduced with either earplugs or a white noise machine. Finally, a comfortable mattress（床垫）and pillows are essential to a good night's sleep.
What is the passage mainly about?
A、How to get a sound sleep.
B、How to lower body stress.
C、How to regulate internal clocks.
D、How to manage anxieties.
【正确答案】：A
【名师解析】:这篇文章主要讨论了如何获得良好的睡眠。文章首先指出，当一个人的生物钟得到调节时，就会发生深度睡眠。接着，文章提出了一些常见的问题，比如许多人因为睡眠时间不固定而导致睡眠问题，并给出了解决方法，比如每天同一时间上床睡觉和起床，以及早上起床后享受15分钟的阳光照射以改善生理节律。文章还提到了睡前例行公事的重要性，比如降低灯光亮度、放松身心、阅读书籍或听平静的音乐，以及洗个温暖的烛光浴或喝一杯热牛奶来帮助进入深度睡眠。此外，文章还讨论了压力对睡眠的负面影响，并提出了一些降低压力的方法，如日常锻炼、写日记、深呼吸练习和逐步肌肉放松。文章还提到了电子设备发出的光线可能导致睡眠问题，并建议在睡前至少一小时关闭这些设备，并降低晚上这些设备的背光亮度，以帮助更快入睡并保持睡眠。最后，文章指出一个完美的卧室有助于甜美的睡眠，建议降低房间温度、使用遮光窗帘或睡眠面罩、使用耳塞或白噪声机来减少噪音，并强调了舒适的床垫和枕头对良好睡眠的重要性。因此，根据文章的主要内容，正确答案是选项A，即如何获得良好的睡眠。