回答问题 阅读短文，然后很据短文内容，简要回答下列问题。
Life today is much easier than it was hundreds of years ago, but it has brought new problems. One of the biggest is pollution. To pollute means to make things dirty. Pollution comes in many ways. We see it, smell it, drink it and even hear it.
Man has been polluting the earth. The more people, the more pollution. Many years ago, the problem was not so serious because there were not so many people. When the land was used up or the river was dirty in one place, man could move to another place. But this is no longer true. Man is now slowly polluting the whole world.
Air pollution is still the most serious. It's bad for all living things in the world, but it is not the only one kind of pollution. Water pollution kills our fish and pollutes our drinking water. Noise pollution makes us angry more easily.
Many countries are making rules to fight against pollution. They stop people from burning coal(煤) in houses and factories, and from putting dirty smoke into the air. Pollution by SO2 is now the most dangerous kind of air pollution. It is caused by heavy traffic. It is sure that if there are fewer people driving, there will be less air pollution.
The earth is our home. We must take care of it. That means keeping the land, water and air clean.
Is our life much easier than it was hundreds of years ago ?
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Why was the pollution not serious many years ago?
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What kinds of pollution are mentioned in the passage?
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How do they fight against pollution in many countries?
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What is the passage mainly about?
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