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题库 / Prep2012-CR-30
In preparation for a large-scale tree-planting project, Thomasville has recorded the location, species, and condition of every tree in its downtown area. The results will be compared with results of the last such tree census, taken 20 years ago. Planting trees primarily from the species that turns out to have the best record of survival will assure downtown Thomasville of an abundant tree population 20 years from now.
Which of the following, if true, most seriously undermines the claim that the tree-planting proposal will assure an abundant tree population?
Because of strict laws governing industrial development, environmental conditions in Thomasville are unlikely to become harsher for trees than they have been during the last 20 years.
Thomasville has reliable records to show which trees in existence 20 years ago were cut down to permit new construction downtown.
A number of trees from one of the species widespread in Thomasville 20 years ago reached the end of their natural life span in the intervening period.
Very few species of trees grow as well in urban conditions as in natural conditions.
A city with a high proportion of any one species of trees can have its tree population devastated by one outbreak of a disease.
错选C（典型问题啊！！！不能再错了！！！）
人家这个城市的目标就是未来20年树的数量多！ 你C在这说上一个20年的调查里有些树不到20年就自然死了达到寿命期限了。没错啊！人家这个城市就是要筛掉这些因为各种各样原因活不满20年的，管你是因为没长好还是因为长好了但是时间到了。没活够就是没活够。
E直接指出了要害：你这筛选出来活得最好的，按理来说可以让整个树群活得更好，但是会出现上一个实验中没有涉及到的问题，太单一的品种会让病传播得更快。
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