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.

为什么答案是C？

我的理解是题目将说去年8月非人为导致的air crush以后，各种关于严格report mechanical problems的法律法规严格起来了，导致report增加了50%。题目关键是说法律法规导致的report增加。

A。飞机还是safe，虽然report增加。 题目并没有提到safe的问题，而且没有具体支持飞机是safe的
B。 错，原因是因为法律法规
C。 mechanical problems没有增加50%（这句说变相再说， 增加的50%不是因为mechanical problems真的增多了，而是因为regulation等）
D.错，正好和题意相反，其实因该是more likely to report under regulation
E。增加的report是因为比较好检测problem了。错，至少题目没有提及。

其实我觉得这道题用排除法就比较好。因为C也是有漏洞的，因为不能证明这法律法规导致增加report并不一定是正好50%,也许更多，或者更少。

如果写错的话，请后面同学补充，谢谢～～