求翻译：在接下来的二十年里，在非洲和亚洲城市居民的人数预计将翻一番。农村人口将会下降，并因为人们放弃农村，平均出生率和家庭的规模也会随之缩小。2050 年，联合国项目中，全球人口将达到 90 亿，与同年，超过 70%的世界人口将生活在城市。是什么意思？

In the next two decades, the number of urban residents in Africa and Asia is expected to double. The rural population will decline, because people abandon rural areas, the average birth rate and family size also shrinks. In 2050, the project of the United Nations, global population will reach 9 bill

In the next 20 years, and, in Africa and Asia the number of city residents are expected to be doubled. Rural population will decline and abandonment of rural people, the average birth rate and the size of families will be reduced. In 2050, the United Nations, world population will reach 100 million,

In meets down in 20 years, in Africa and the Asia city people's population estimated will double.Rural population will be able to drop, and because the people will give up the countryside, the average birth rate and the family scale will also be able along with it reduction.In 2050, in the United Na

Over the next 20 years, the number of urban residents in Africa and Asia are expected to double. Rural population is expected to decrease, and as people abandon rural, average fertility rates and family size also narrowed. In 2050, the United Nations projects, the global population will reach 9 bill

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