Enough sleep is important to health. The amount of sleep needed    (depend) on the age of the person and the conditions in    sleep takes place. The young may need more sleep than _old, but usually eight hours are enough for the health of grown-ups. Some can do with less than this amount,    others may need more. Every person knows his own need.  is then a matter of good judgment to satisfy his need. Sleep should always be enough to make one bring back his   (strong) and get ready for a day’s work.
Fresh air is necessary to sound sleep. So it is not without reason for some people to think that it is practicable(切实可行的) to sleep the open air. A bath at bedtime,  hot nor cool but of body temperature, may be _ (help) to sleep. Sleep producing drug(帮助睡眠的药物) should never be taken except when __(suggest) by a doctor.