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.
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