源语言: 英语
The size of population changes as babies are born and people die.When there are more new babies then deaths,the population grows. The population will stop growing only when fewer babies are born. Today, about 90 million people are added to the world population every year . The main reason for this huge growth in population is a drop in the rate of death .Fewer babies and children are dying young , and adults are living longer than ever before. Sewers and clean water supplies have improved sanitation. Fewer people , especially babies , now become sick and die from drinking polluted water . New drugs and medical treatments also have helped reduce death rates.
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