Today， pollution has become a serious problem to us. It means that the air， seas， rivers and land are polluted by waste or poisonous things. It does harm not only to human beings but also to animals （It does harm to animals， as well as human beings.）。We cannot have fresh air because many factories have the poisonous smoke sent into the air. Beautiful parks are made dirty by plastic tins and bags. Fish die from the polluted water. It is said that strange diseases have appeared in some places because of pollution.I hope scientists can find ways to solve the serious problem. We are looking forward to seeing the clear sky， clean rivers and beautiful parks again.