题目内容
Enough sleep is important to health. The amount of sleep needed depends on the 1 of the person and the condition 2 sleep takes place. The young may need 3 sleep than the old, but 4 eight hours are enough for the health of grown-ups. Some can do 5 less than this amount but children may need more. Every person knows his own need. It is then a matter of 6 satisfy it. Sleep should always be enough to make one 7 and ready for a day's work.
8 is necessary to sound sleep. It is not without reason for some people to 9 that it is practical to sleep in the open air. When a person can 10 himself warm, out-of-door sleeping probably gives the body 11 commplete relaxation.
Ability to sleep is largely a habit. The conditions 12 to only lead to sleep. Out-of-door exercises, a good 13 of regular hours and the avoidance of the late eating and smoking are all helpful to sound sleep. 14 factors are 15 within the control of any person. 16 at bedtime, 17 hot nor cold 18 body temperature, may be helpful to sleep. Sleeping pills should never be 19 except when 20 by a doctor.
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解析：
