PREP_26

qiqiusa

PREP_26

26.   (31045-!-item-!-188;#058&004365)

 

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.

正确答案为：B

为什么A不对，因为我感觉B中说的a steadily declining正在稳定下降的出生率，出生率下降，人口应该增长啊，这并不能解释人口为什么没有增长的矛盾啊。而A中说，过去是医疗卫生条件差，而现在是车祸多导致了死亡多，这不是正好解释了人口为什么不能上升的原因。

我感觉A对，请哥哥姐姐分析一下为什么正确答案B对？谢谢……

wycg

B: if Mortality rate keeps in a stable level, and birth rate does not increase dramatically, then, the population growth can not change markedly. 

dustyrick

my take on this is : after you narrowed them down to A and B , it then depends on what scale of assumptions you need to make in each case.

for A, current mortality rate VS a static reference
for B, you have something /s^2 which clearly shows a trend

now you can choose,   ^^



  

qiqiusa

Ok, 明白了……