题目内容：

Hundreds of years ago，life was much harder than it is today.People didn't have modern machines then.There was no modern medicine，either.

Life today is better than it used to be，but at the same time，new problems come up.One of the biggest problems is pollution.Water pollution has made our rivers and lakes dirty.It kills fish and pollutes our drinking water.We have to talk louder because of noise pollution and it also makes us angry more easily.Air pollution is the most serious kind of pollution.It's bad for all living things in the world.

Cars，planes and factories all pollute our air every day.Sometimes the polluted air is so thick that it is like a quilt over a city.This kind of quilt is called smog.

Many countries are making rules to fight against pollution.Factories must deal with the waste water before it is thrown away.They mustn't blow heavy smoke into the air.

We need to do many other things.We can put the waste in the dustbin instead of throwing it on the ground.We can go to work by bus or with our friends in the same car.If there are fewer people driving，there will be less pollution.

1.What can make people angry more easily？(不超过5个词)

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2.What is smog according to the passage？(不超过15个词)

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3.What's the main idea of this passage？(不超过15个词)

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