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“绿色奥运”，拒绝兴奋剂．乙基雌烯醇是一种参赛运动员禁用的兴奋剂，其化学式为C20H32O，下列关于乙基雌烯醇的说法中正确的是（　　）

A．它属于混合物

B．一个分子中含有16个H2单质

C．分子中C、H两种元素的质量比为5：8

D．它由三种元素组成

答案

答案：D

完形填空

根据短文内容及所给首字母提示写出所缺单词, 并将完整单词填在下面对应题号后的横线上。

Air is very important to everything that lives. But the air we breathe is g  1  dirty. People all over the world are looking for w  2  to make it clean again.

Have you e  3  watched the smoke from chimneys(烟囱) rising high in the air? Have you s  4  the smoke from cars and trucks on roads or the smoke from planes? The smoke is not g  5  to breathe. If we want to keep healthy and strong, we need to breathe c  6  air.

W  7  more and more factories everywhere and more and more cars, trucks and planes, it is getting harder and harder to do with the air p  8 .

Scientists have a  9  taken actions to stop or slow down some of the things that make the air dirty. They will not stop working u  10  we have clean air again.

1.           2.           3.           4.           5.        

6.           7.           8.           9.           10.        
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名词解释

花纹失真
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