The earth is our home. We must take care of it. Life today is easier but there are some new problems. One of the biggest problems is pollution. Pollution comes in many forms. It is beginning to harm our health and even our life. Many years ago, the problem was not so serious because there weren’t so many people. In other words, the more people, the more pollution. Now man is slowly polluting the whole world. Air pollution is still the most serious. It’s not good for living things in the world. Many countries don’t let people burn anything bad for air in houses and factories in the city. SO2 is now the most dangerous pollution. It’s partly caused by heavy traffic. People say it’s best to ride a bicycles are expensive or people are tired. It’s because cars are more convenient(方便的），so more people go to work by car, and then the situation is getting worse and worse. We should make it so difficult and expensive for drivers to drive their cars into the city. They will go back to use their bicyc