Enough sleep is important to health. The amount of sleep【C1】______depends on the age of the person and the conditions in which sleep【C2】______The young may need more sleep than the old, but【C3】______eight hours is enough for the health of grown-ups. Some can do with less than this amount but【C4】______may need more. Every person knows his own need. It is then a matter of how to【C5】______it. Sleep should be always enough to make one relaxed(松弛)and ready for【C6】______work.  Fresh air is【C7】______to sound sleep(酣睡). It is not【C8】______reason for some people to insist that it is practical to sleep in the open air.【C9】______a person can keep himself warm, out-of-door sleeping probably gives the body【C10】______complete relaxation.  Ability to sleep is largely a habit. The conditions referred to only lead to sleep. Out-of-door【C11】______, a good habit of regular drinking and the avoidance of late eating and【C12】______are all helpful to sound sleep. Such factors are largely within the【C13】______of any person. A bath at【C14】______, neither hot nor cold but of body temperature, may be helpful to sleep. Sleeping pills should never be taken except when suggested by【C15】______

The amount of sleep【C1】______depends on the age of the person