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题库 / Prep2007E1-CR-26
The population of Megacity, a sprawling metropolis in Remsland, has grown at a fairly steady rate for over a century. A hundred years ago, poor sanitation in the city caused high mortality rates among the city's inhabitants, and what fueled the population increase was immigration from rural villages. This immigration has continued and even increased. Moreover, in recent decades, city sanitation has improved enormously. Yet the city's population growth has not significantly accelerated.
Which of the following, if true, most helps to explain why the city's population growth rate has not changed?
Mortality rates that were associated with poor sanitation in Megacity a hundred years ago were orders of magnitude higher than are mortality rates associated with vehicular traffic, which is currently a major cause of death in the city.
For several decades, Megacity, as distinct from the countryside, has had a steadily declining birth rate.
Cities smaller than Megacity have also experienced sustained population growth.
The great majority of immigrants to Remsland settle in Megacity, at least initially.
Megacity has long offered better employment prospects than most rural areas.
现象解释：为什么在继续有增加的移民涌入城市，并且卫生条件改善的情况下。城市的人口增长没有显著增加
错选choice A, 很多年前因为糟糕的卫生条件引起的死亡率，是现在因车祸造成的死亡率的好几个数量级-> 更没法解释为什么
正确B，出生率降低了，所以人口并没有加快增长。（插入语 as distinct from the countryside与乡村截然不同，不用管这句话）
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