阅读理解。
Air is very important to everything that lives. But the air we breathe (呼吸) is getting dirty. People all
over the world are looking for ways to make it clean again.
Have you ever watched the smoke from chimneys (烟囱) rising high and spreading (散布) out in the air?
Or seen the smoke that puffs (喷出) from cars and trucks on the road? Or watched the smoke trailing (从后
面喷出) from a jet plane?
Sometimes smoke looks pretty in the air. But it is not good to breathe. If we are going to keep well and
strong, we need to breathe clean air.
With more and more factories everywhere and more and more cars, trucks and planes, it is getting
harder and harder to keep our air clean.
Scientists have already found ways to stop or slow down some of things that made the air dirty. They
will not stop working till we have clean air again.
1. The air we breathe is getting _________.
A. dirty
B. clear
C. clean
2. Air is important to _________.
A. everything
B. animal
C. every living thing
3. The smoke that sometimes look pretty in the air is _________ to breathe.
A. good
B. will
C. not good
4. We need to breathe clean air to keep _________.
A. clean
B. good
C. well and strong
5. Scientists will not stop working _________ we have clean air again.
A. while
B. till
C. when