短文填空。
根据下面短文内容，在空格处填上一个恰当的词，使短文完整、通顺。
The world is divided （分为）into ___main parts .The difference is that one part is rich and the ___ is poor. In the poor part, a lot of people never get enough to eat. In the rich part, a lot of people ___ too much. In one part , children starve （饿死）and in the other , a lot of people get ____ and fatter and have to go on diets （节食）, or do special exercises in order to lose weight.
The poor countries have special ____. Sometimes the land is too poor to grow anything on . The land can be improved （改善）, but a lot of things must be done first . The people must be educated and water must be found. But the rich countries have problems, ____. There are not always pleasant places to live in . Sometimes the air is too dirty to breathe, and the rivers are too         to swim in or to take water from. The roads are too crowded to drive along. Large numbers of people do not have decent （像样的）houses to live in. Some things will have to be done about these problems.
The air and the river will have to be cleaned, ____more houses will have to be built.