_______(50)A. This allowed scientists to gauge th
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_______(50)
A. This allowed scientists to gauge the pace and progress of the ecological recovery.
B. Yet in other businesses,such as farming and property development,ant surveys aren’t used widely.
C. Employing those people are expensive.
D. They do this by sorting the ants,counting their numbers and comparing the results with those of earlier
surveys.
E. The evolution of ant species may have a strong impact on our ecosystem.
F. Others will die out for lack of food.
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答案：C
空前一句“many companies can’t afford the expense or the laboratory time needed to sift results for a comprehensive survey”讲到很多国家不能付出高额的费用，研究蚂蚁的专家稀少，故C项“雇佣他们花费巨大”与上文联系紧密，符合语境。