Pollution

With the development of the techniques, people are living better and easier lives, but meanwhile, pollution becomes an important worldwide issue. The earth we live on is not the one we had before. The air is all consist of poisonous gases. The sky is not as blue as it was before. The rivers are not as limpid any more. The amount of animals is decreasing. The temperature of the earth is increasing every year and the cities are full of dirt, noises, garbage, and pathogens.

There are many kinds of pollution: air pollution, water pollution, nuclear pollution, and so on. Air p...