07prep1-26

hebelong

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?

(A) 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.

(B) For several decades, Megacity, as distinct from the countryside, has had a steadily declining birth rate.

(C) Cities smaller than Megacity have also experienced sustained population growth.

(D) The great majority of immigrants to Remsland settle in Megacity, at least initially.

(E) Megacity has long offered better employment prospects than most rural areas.

oa: B,能详细说说么？我错选A了，谢谢各位的帮助

sdcar2010

This is a math problem for a paradox question.

This year's total population = Last year's total + new immigrants + new borns - whoever move out - whoever died

B) simply says that the new borns number is so low that that even coupled with new immigrants coming, they cannot compensate for the loss in the other two categories.

hebelong

A提及人员死亡数但无B直接，所以选B了？

sdcar2010

A) The death rate was higher before than now. This would not help the conclusion at all.

rikihsu

我感觉是。。

a) 之前死亡率主要是卫生设施，现在主要交通事故。。并不能解释。。
b) 出生率很低 ，那么移民人数还增加，因为卫生设施死亡的人数少了，但是会影响整个人口数量。

就像LS说的人口=原有人口+出生+移民-死亡- 移出
要人口不猛增，你要么+的项目减少，要么-的项目增加。

hebelong

哦~~~~~~·我明白了~谢谢你们哦！