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Air is very important to everything that lives. But the air we breathe is g  小题1:  dirty. People all over the world are looking for w 小题2:  to make it clean again.
Have you ever watched the smoke from chimneys(烟囱) r 小题3:  high in the air? Have you s  小题4:___ the smoke from cars and trucks on roads or the smoke from planes? The smoke is h 小题5:  to everyone, especially old people and children. If we want to keep well and strong, we need to breathe f 小题6:  air.
With more and m  小题7:  factories everywhere and more and more cars, trucks and planes, it is getting harder and harder to do with the air p 小题8:  .
Scientists have a小题9:  found ways to stop or slow down some of the things that make the air dirty. They will not stop working u 小题10: we have clean air again.