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    There are many kinds of pollution around us, 1 air pollution, soil pollution, noise pollution and light pollution. They are bad 2 our health in many ways.

    Burning gas, oil and coal creates air pollution. It can cause some eye and breathing problems.

    With the 3 of pollution and the development of industry, litter is everywhere. It makes our environment dirty. People put lots of rubbish in the land. Farmers use too many 4 in the fields. They destroy the soil.

So soil pollution has become serious.

    Noise pollution can make people 5. For example, people may lose their hearing if they have worked in a 6 place for a long time. Too much noise can cause high blood pressure 7.

    Having worked for a long time in strong, changeable light 8 cause some kinds of illnesses. It makes people feel 9 and is especially bad for the eyes.

    With 10 pollution, our planet will become greener and our health will be better. Let's be greener people.

    Is the world too crowded? Well, that's a hard question to answer. It's a matter of perspective(视角). In Montana, you might drive for a mile in any direction and not see another human being. In Macao, about 50, 000 people live in every square mile!

    What is true is that the world's population doesn't stay the same. It has been increasing at a very fast rate. That's in part because in each generation(代) there are more people who would like to have children than those in the last generation.

    Five hundred years ago, the population of the world was about 425 million. Right now it is doubling every 40 years. That means, if this rate of growth continues, when you are a parent, there will be twice as many people on the earth as there are now. Wow! That's a lot of people! Soon the world's population will probably reach 8 billion. Some people worry about that! But there is a lot of disagreement about the view that how many people on the earth equals(相当于) too many people. But everyone agrees that the more people there are, the more resources the world needs to feed, store and take care of, and the more need there is to think carefully about how we live and use the earth's resources.