请教费费CR中的61题

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. 

小弟一直不明白为什么答案是C，有请各位给解释下，谢谢！

我用的排除法：

A 说飞机旅行很安全，地球人都笑了...

D 说航空公司比以往报告机械故障要迟钝很多，刚好说反了。不过这里其实是个暗示，强调了”REPORT“

E 说8月份以来机械故障更容易被发现，这个文章没体现出来。

B是个干扰选项，丫说8月机械故障增长巨快，而文章说的是”reports of airplane mechanical problems“增长了50％，而为啥REPORT增长了这么多呢，文章说了，原因（That accounts for）是”new and more stringent rules “开始施行了。这就暗示了报告的增多是因为新的规定更加严格了，原来不需要报告的机械故障现在都要报告了，所以报告才增多了。

解题逻辑：

1）并非所有机械故障都会导致事故，所以没有写报告的小的机械故障数量是未知的。

2）报告的多少取决于需要写报告的标准（就是说对什么样的机械故障要进行报告）。

3）故障报告的多少不直接等于故障的多少。更严格的规定会导致很小的机械故障也要写报告，所以从数量上看报告增多了，而实际故障变化无法体现。