The world is divided (分) into two parts. One half of the world is rich and         is poor. In the poor part, a lot of people have never got enough to eat. When they are ill,        the hospitals can receive them because they have no enough           . In the rich part, a lot of people          too much. For example, a dog or a cat in North America eats more than a child in poor countries.
The poor countries have some other difficult problems. Sometimes the land is too poor to grow           on. People there don’t have rich land or enough water. The land can be made better, but a lot of things must be done. The people         be taught and water must be found.
But rich countries have problems. too. There’re not good places to         . Sometimes the air is not clean and the rivers are too dirty to swim in or drink. The roads and streets are full of people and buses. Cars and buses have to move         . Noise is too much. Some people don’t have houses. People must do something about the problems.
People must clean the air and the rivers, and they must         them clean. People have to build more houses.        we can’t do these things easily.