5.What does
“Clear” allow you to do when you press it?
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Passage 30
No one knows
why we sleep, but it’s certain that we need to. People who are prevented from
sleeping begin to suffer obvious effects after a few days-they think less
clearly, and they fall asleep during the working hours.
There are no
rules about sleep. Generally speaking, grown-ups sleep about 7 and a half hours
each night and probably more than 60 percent get between seven and eight hours.
But perhaps eight percent are quite happy with 5 hours or less, and four
percent or so find that they want ten hours or more. If you feel all right,
you’re probably getting enough sleep. The important thing is not to worry how
much other people get-their needs may be different. Exercise doesn’t seem to
increase the need for sleep-office workers, for example, sleep for about as
long as people doing physically active work.
Children
sleep more than grown-ups-perhaps 14 to 18 hours soon after birth, going down
to grown-up levels by early teenage (青少年). Sleep patterns also tend (倾向) to be different in the old people, who may sleep less at night than they
did when younger, find sleep getting more broken, and often make it a rule to
sleep during the daytime.