求解： Prep 1 - 17

joshi

17.
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.  lants 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.

答案是D
看了答案，勉强理解。但做题时，思路并不会往D靠。因为题目中没有地方提及关于Heavy vehicular traffic will reduce light的意思。求解题思路，谢谢！

wlf1987

城市和乡村差在sulfur dioxide ，温室避免了这一差异，但是结果为什么还不一样呢？
D给出了需要考虑的评价因素——阳光被遮住了，这导致结果差异

根儿哥1989

首先这个题的结论是一个比较句，因此再看选项的时候优先选择看比较句。并且要比较比较的对象是否有意义。
A陈述的是一个事实，并且仅仅指出了城市的状况，没有与RURAL作比较。
B无关的比较 greenhouse 和OUTDOOR比较没有意义
C无关
D出现了新的元素VEHICLE，并且说是DEPOSIT GRIME ON GREENHOUSE WINDOWS.因此阻碍了palnts的生长。正确
E地点变换了，变成了school，因此错误

根儿哥1989

up，求拍砖

joshi

谢谢！