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? | 
