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题库 / Prep2007E1-CR-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. 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?
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.
At both schools, the plants in the greenhouses grew much more quickly than did plants planted outdoors in plots near the greenhouses.
The urban class conducting the experiment was larger than the rural class conducting the experiment.
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.
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.
城市空气比农村空气含有更多二氧化硫，城市的植物比农村植物长得慢。在一个实验中，测试因为二氧化硫对生长造成影响有多不一样，城市和农村学校的班级在学校的温室中种植物，过滤温室空气去除二氧化硫。城市温室中的植物比农村温室中生长更慢。
评价题， 实验中排除了二氧化硫的影响，如果两地植物生长一样，则说明了实际二氧化硫影响大；如果城市植物仍生长慢，肯定是有除二氧化硫以外其他因素导致生长慢
A 城市学校位于二氧化硫水平远低于典型城市地区的位置；比较是在温室无二氧化硫的环境下，所以学校在含二氧化硫低的位置无关， 排
B 两校，温室中植物比温室外的植物生长快很多；文中实验是比较两地温室的对比，而非室内室外的对比，且这是是说明二氧化硫有影响，无法解释除去二氧化硫后两地生长速度的差异，排
C 城市实验比农村实验大；无关
D 城市严重的汽车交通持续的堆积灰尘在温室窗户上，减少了植物的光照；其他因素导致生长不同，可作为评价考虑依据，正确
E 因为城市二氧化硫含量高，城市的温室空气过滤比农村更有效率；城市温室过滤器更有效率，二氧化硫含量应该少，无法解释城市植物生长慢，排
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