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?
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?
B D
(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.
2. 本题的结论是plants in cities typically grow more slowly than do plants in rural areas。所以这是一个很典型比较型结果,所以我们的evaluate必须也存在比较,而注意——这是植物的生长在城市和农村的比较,所以我的evaluate需要存在这个元素。
3. 而D,我们可以看到Heavy vehicular traffic 是城市相对独有的,农村相对没有的,而Heavy vehicular trafficsuch 是constantly deposits grime on greenhouse windows,说明这种现象是在城市客观长期存在的,足以代表城市,而最为关键的就是reducing the amount of light that reaches the plants inside. 这里很明确地涉及了一些自然科学原理,因为阳光对于植物生长是会起到足够影响的。所以D在这里等于是提出了他因,除了通过filtered the greenhouse air会让其生长缓慢,阳光也是一个因素。起到了评价的作用。
4. 而B,则显然不存在城市和农村的比较,而且,B只能起到对于filtered the greenhouse air会不会使植物生长缓慢的评价,与题意不符
我也是选B,现在想明白了B实际上是不相关的。而D通过一个全新的原因推出了结论,文中实验结果的原因事实上是缺条件的,也就是说没有光照这个条件是得不出这个实验结果的,根据问题most important to take into account in evaluating the result? 就明白了。