FeiFei-61

61. Investigators concluded that human failure was not responsible for the fatal airplane crash last August, and since that time new and more stringent rules for identifying and reporting mechanical problems have been in effect. That accounts for the fact that reports of airplane mechanical problems have increased in frequency by 50 percent since last August.

Which one of the following is an assumption underlying the argument in the passage?

(A) Airplane travel is still relatively safe, despite the increase in reported mechanical problems.

(B) Mechanical problems in airplanes have increased dramatically since last August.

(C) Mechanical problems in airplanes have not increased by 50 percent since last August.

(D) Airlines are less reluctant to report mechanical problems than they previously were.

(E) Mechanical problems in airplanes have become easier to detect since last August.

答案是C,谁能告诉我为什么?

assumption:

对C取非，就是mechanical problems have increased by 50 percent since last August, 那么与the fact that reports of airplane mechanical problems have increased in frequency by 50 percent since last August 一致，就削弱文中结论rules count for the reported increased rates,也就是说rules of reports 对这个报告结果没有作用。