求助一道PREP逻辑题哇~~~

Mariana1989

这道题为什么选E不选B呢？要看二氧化硫对植物生长的影响，用温室里的和温室外的比较为什么不行呢？？
求解答哇~~~感激不尽~~
Urban air contains more sulfur dioxide than does rural air, and plants in cities typically grow more slowly than do plants in rural areas.In an experiment to see how much of the difference in growth is due to sulfur dioxide, classes in an urban and a rural school grew plants in greenhouses at their schools and filtered the greenhouse air to eliminate sulfur dioxide.Plants in the urban greenhouse grew more slowly than those in the rural greenhouse.

Which of the following, if true, would it be most important to take into account in evaluating the result?

(A) The urban school was located in a part of the city in which levels of sulfur dioxide in the air were usually far lower than is typical for urban areas.

(B) At both schools, the plants in the greenhouses grew much more quickly than did plants planted outdoors in plots near the greenhouses.

(C) The urban class conducting the experiment was larger than the rural class conducting the experiment.

(D) Heavy vehicular traffic such as is found in cities constantly deposits grime on greenhouse windows, reducing the amount of light that reaches the plants inside.

(E) Because of the higher levels of sulfur dioxide in the air at the urban school, the air filters for the urban school's greenhouse were changed more frequently than were those at the rural school.

cdwayne

題目要求evaluate實驗結果(Plants in the urban greenhouse grew more slowly than those in the rural greenhouse)，因此答案可能支持可能反駁。

(D) 反駁，有其他因素參與無法確認二氧化硫是否為真因。

廖良燕

见鬼。我也是选B。更悲催的是，就是不明白为什么选E。请高手解答。

sandychen168

题目中说了，为了找出是否是SD导致的plant在城市里长得慢，所以进行的这个实验。而为了达到这个目的，他们filtered the greenhouse air to eliminate sulfur dioxide，说了eliminate就是消除。
但是即使这么做了，城市里的plant还是比rural里的plant长得慢。那么是不是就能得出是SD导致的plant长得慢呢？

还不行，为什么？因为如果我换的不勤，那么就可能eliminate的就不那么彻底，不能与rural的空气质量相比，那么可能城市里plant长得慢还是由SD导致的，而不是本身plant在city就长得慢