求翻译：世界人口快速增长，带来了许多问题，如环境污染，失业人数的增长，城市的拥挤等。中国是一个人口大国，已经采取了政策来控制人口增长：实行计划生育政策是什么意思？

World population growth has brought many problems, such as environmental pollution, the growth of unemployment, the city's crowded and so on. China is a populous country, has adopted a policy to control population growth: family planning policy

World population growth has brought about many problems, such as environmental pollution, the number of the unemployed, the growth of cities such as overcrowding. China is a country with a large population, has taken the policy to control population growth: family planning policy

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Rapid population growth in the world, has brought a lot of problems, such as environmental pollution, growth in the number of unemployed, urban crowding, and so on. China is a populous country, has adopted a policy to control population growth: family planning policy

World population increases fast, has brought a lot of questions, such as the environmental pollution, growth of the total unemployment, crowdedness of the city,etc.. China is a large country in population, has already adopted the policy to control population growth: Implement family planning policy