题干

如图所示是四冲程汽油机的一个工作循环示意图,其中属于做功冲程的是(  )

A:

B:

C:

D:

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答案(点此获取答案解析)

B

同类题4

阅读下面短文,从短文后所给的A、B、C四个选项中选出最佳选项,以填入空白处的最佳选项。    

    "Sesame Street" is a TV programme for children. It first appeared in New York 1 1969. It is called "the longest street in the world". That's because the TV programme by that name can be seen in so many parts of the world.

    In the US over six million children watch the programme regularly. The viewers include more than half the nation's pre-school children. Parents love the programme. Many teachers also think it is very helpful, 2 some educators are against certain things in it.

    Tests show children from different background have benefited from watching the programme. Those who watch it five times 3 week learn more than those who watch it once in a while.  In the US the programme is shown at 4 hours so that more children can watch it. The programmes all 5 songs, stories, jokes and pictures to help children understand numbers, letters and human relationship. But there are some differences. For example, the programme made in Mexico City devotes more time to teaching whole words than to teaching letters one by one.

    Why is "Sesame Street" more successful than other children's shows? There 6 many reasons—the good education of its producers, the support 7 the government and businesses, and the skillful use of many TV tricks. Also 8 watch it with their children. This is partly because famous adult stars often appear on it. But the best reason may be that it makes every child 9 able to learn. Children find themselves learning, and they want to learn 10 .