【答案解析】Cities have been destroying the environment around them and have often paid the price for it. Scientists have noticed that an old city was buried in mud for thousands of years just because it was submerged by the flood produced by deforestation. Furthermore, many problems will be brought to its citizens by cities. It is estimated that in human history the number of population in city will have outnumbered those living in the rural areas for the first time by the year 2050. Within the following 30 years, the life quality of next generations and the opportunities of solving the internal and external conflicts will depend on whether the methods can be found by governments to control urban development acceleration.