how to protect the environment has become one of the biggest problems in the world. there are many kinds of pollutions around us, such as air pollution, noise pollution, water pollution and light pollution. we can find that rubbish not only pollutes our environment but also harms people's health. so we should not throw rubbish everywhere. some factories pour waste water into the rivers and the lakes. the behavior of these factories will pollute the water , and sometimes it can kill the fish living in them.