50 Airline: Newly developed collision-avoidance systems, although not fully tested to discover potential malfunctions, must be installed immediately in passenger planes. Their mechanical warnings enable pilots to avoid crashes.

Pilots: Pilots will not fly in planes with collision-avoidance systems that are not fully tested. Malfunctioning systems could mislead pilots, causing crashes.

The pilots’ objection is most strengthened if which of the following is true?

(A) It is always possible for mechanical devices to malfunction.

(B) Jet engines, although not fully tested when first put into use, have achieved exemplary performance and safety records.

(C) Although collision-avoidance systems will enable pilots to avoid some crashes, the likely malfunctions of the not-fully-tested systems will cause even more crashes.

(D) Many airline collisions are caused in part by the exhaustion of overworked pilots. C

(E) Collision-avoidance systems, at this stage of development, appear to have worked better in passenger planes than in cargo planes during experimental flights made over a six-month period.

Answer is C. 选出C并不难. 我的问题是如何排除A. 我的理解是: 选项A强调Malfunctioning systems 是成立或有意义, 因而支持了结论(Malfunctioning systems导致crashes).

A的支持作用不如C明显, 但感觉,总是有一点支持. 是不是GMAT的逻辑, 也象改错一样, 有effective和corrective之分呢?

A应该是无关的选择吧，mechanical devices to malfunction指的是机械故障，而 mislead pilots是机械起到误导的作用，并不是故障啊。

谢谢回复. 但我还是不大清楚.

换个说法:

司机说: 我不开这辆新的宝马车的, 因为它的刹车没有经过完全的测试, 刹车系统的可能的故障会误导我, 导致我撞车.

路人说: 机械系统总是有可能发生故障的.

如果路人说的是正确的, 机械系统总是有可能发生故障, 那么刹车系统是有可能发生故障的. 这个说法为什么不能支持司机的观点呢?