20．Dad hurried to get home before dark so he could go for a run，but he had forgotten to wear his safety belt-a mistake 75% of the US population make every day．Maybe ten-year-old Elizabeth put it best when she said to her father，"But，Dad，you can't be healthy if you're dead．"The big question is why so many people drive cars without wearing safety belts．
There have been many misunderstandings about safety belts ever since their first appearance in cars about forty years ago．The following are three of the most common．
Number One：Safety belts aren't needed at speeds of less than 30miles per hour．
Truth：When two cars traveling at 30mph hit each other，an unbelted driver will hit himself on the front window of the car with a hard force，it feels like diving headfirst into the ground from a height of 10meters．
Number Two：Safety belts"trap（困住）"people in cars．So if the cars are burning or sinking in water，it's difficult for people to move．
Truth：Sorry，but studies show that if people are not wearing safety belts，they are easy to be knocked unconscious（昏迷）．So they will have a greater chance of dying in these accidents．People wearing safety belts are usually protected to have a clear head to free free themselves from such dangerous situations，not to be trapped in them．
Number Three：It's best to be"thrown clear"of a serious accident．
Truth：Sorry again，but any accident serious enough to"throw you clear"is also going to be serious enough to give you a very bad landing．Studies show that chances of dying after a car accident are twenty-five times greater when people are"thrown clear．"
21．From the first paragraph the writer want toC．
A．discuss the US population．
B．express a daughter's love．
C．show a problem of driving
D．introduce main characters．
22．The picture which means"safety belt"isA．
23．It．proves thatD when two cars hit at 30mph．
A．cars won't be pulled to a workshop
B．people will not be knocked seriously
C．it's like diving into the water from 10meters high
D．it may cause a serious accident without protection
24．We can learn from the passage thatD when someone is"thrown clear"．
A．his life will be saved
B．nothing will be belt in the car
C．it turns out a better ending
D．it increases the chances of dying
25．The passage mainly tells us that people shouldB．
A．free themselves when in danger．
B．wear the safety belts while driving
C．drive a car at the right speed．
D．have a clear head in an accident．
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