这个逻辑题中的实验是怎么一回事啊？

dzxu

17.    (27669-!-item-!-188;#058&003302)    

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：D  

之前做错了。最近重做，还是错了。

哪位高人能指点一下？选D是为了排除他因？

另外，题目中的这个实验：农村和城市的学校都将plant放在温室里，而且filtered the greenhouse air to eliminate sulfur dioxide，这样的话，如何看出sulfur dioxide 的区别？

这个实验有点莫名其妙啊？求解释。

dzxu

自己up一下！

dzxu

再up一下

lizhuang0312

实验是想要知道究竟是不是SD造成了城市植物生长速度比乡村植物慢，因此他们过滤掉了SD做实验，结果发现城市里的植物生长速度还是比乡村的慢，所以造成城市植物生长速度较慢另有他因，D就给出了一个合理的他因，希望有帮助~

hanshipeng

同上，D给出了其他理由--污染的环境造成植物光合作用效果不如rural area.

V3会长

3 4楼解释的很清楚了  这段文字里面已经说明把二氧化硫过滤了，就排除了有关二氧化硫造成影响的选项，也就是说需要找到其他影响植物生长的因素，D选项里面正好说到了由于traffic的原因导致光线不足的原因，所以选择D

dzxu

i see

many thx！！！

dreamistrue

这是个对照实验 说明sulfur dioxide已经不是造成这个现象的原因 所以只能是它因,也就是D-different amount of light" 如果按照E的说话城市的过滤器更换更频繁，那么对二氧化碳吸收能力更好，所以说植物应该长得快嘛，和事实相反了，所以不是那个问题.不选E，选D。 E) on the other hand won't help explaining the unexpected result mentioned above. It only proves that the SO2 in urban air is more than that in rural air. We know that already from the stimulus.

sbdk

个人对于B、D选项的理解
重点在实验的目的： an experiment to see how much of the difference in growth is due to sulfur dioxide


1，实验者想知道 市区和乡村地区植植物生长的速度受二氧化硫的影响程度有多大（而不是受不受二氧化硫影响）。因为实验者假设除了二氧化硫以外还有很多其他的差异因素影响着这两个地方植物的生长，要知道二氧化硫（单一因素）对植物生长速度的影响程度，最简单的办法就是保持其他变量不变，改变二氧化硫含量这个因素。实验其实有两个对照组：X组（测量组，用来测量核心数据）：城市户外植物VS城市温室植物；Y组（修正组，用来寻找实验误差以提高实验的可信度和准确度）：城市温室植物VS乡村温室植物。实验者的目的是通过研究X组的结果，测量出植植物生长的速度受二氧化硫的影响程度有多大。但是现在Y组出现差异，说明出现实验误差，X组的数据可信度降低，不能得出实验结果。


接下来就容易了，最有用的选项显然就是可以提供更多关于Y组结果的信息（D选项）。X组的信息再多再精确（B选项），在没有解决误差问题前都是不能达到实验目的的。




欢迎大家拍砖！～～写完这些发现和我做题时的想法已经是天差地别了。。。