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.