选择题：Sound sleep occurs when one.s internal clock is re

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 longe