Urban air contains more sulfur dioxide than does ruralair, and plants in cities typically grow more slowly than do plants in ruralareas. In an experiment to see how muchof the difference in growth is due to sulfur dioxide, classes in an urban and arural school grew plants in greenhouses at their schools and filtered thegreenhouse air to eliminate sulfur dioxide. Plants in the urban greenhouse grew more slowly than those in the ruralgreenhouse.
Which of the following, if true, would it be mostimportant to take into account in evaluating the result?
(A) The urban school was located in a part of the city inwhich levels of sulfur dioxide in the air were usually far lower than istypical for urban areas.
(B) At both schools, the plants in the greenhouses grewmuch more quickly than did plants planted outdoors in plots near thegreenhouses.
(C) The urban class conducting the experiment was largerthan the rural class conducting the experiment.
(D) Heavy vehicular traffic such as is found in citiesconstantly deposits grime on greenhouse windows, reducing the amount of lightthat reaches the plants inside.
(E) Because of the higher levels of sulfur dioxide in theair at the urban school, the air filters for the urban school's greenhouse werechanged more frequently than were those at the rural school.
A. school located在哪不是新原因。
C: fullerenes是如何形成的，跟检测the state of earth’s crust无关;
A: 是迷惑的选项。confirming矿石含有fullerenes 需要仔细实验，说明要在矿石中发现fullerenes挺麻烦，但是并不能说明发现fullerenes会对检测fullerenes产生影响;
D: fullerenes晶体结构我们不知道，无法从它来了解the state of earth’s crust. 正确答案!