17/57. 

Since the deregulation of airlines, delays at the nation's increasingly busy airports have increased by 25 percent.  To combat this problem, more of the takeoff and landing slots at the busiest airports must be allocated to commercial airlines.

Which of the following, if true, casts the most doubt on the effectiveness of the solution proposed above?

(A) The major causes of delays at the nation's busiest airports are bad weather and overtaxed air traffic control equipment.

(B) Since airline deregulation began, the number of airplanes in operation has increased by 25 percent.

(C) Over 60 percent of the takeoff and landing slots at the nation's busiest airports are reserved for commercial airlines.

(D) After a small midwestern airport doubled its allocation of takeoff and landing slots, the number of delays that were reported decreased by 50 percent.

(E) Since deregulation the average length of delay at the nation's busiest airports has doubled.

A correct, 我选的是C

A还是不太明白，是说题目中的建议实际上隐含了假设就是造成airport忙的原因是commercial airlines. 则A用他因解释，因为天气状况才造成airport忙的。不知道现在想的对不对。有NN 帮忙解释一下吗？

题目的意思是问，abdce中哪一条会让人对文中提出的解决办法的有效性产生怀疑？（真拗口）

也就是说，文中提出的解决办法（增加起落通道），对abcde哪一条是没什么作用的？

这样就选A啦

因为天气原因造成的航班延误是人力无法控制的

航班晚点，空管局认为是非商务起降航班多、旅客多造成，削弱：实际另有他因。

The major causes 据我观察，是重要的他因削弱的正确答案标志词，我发现过不止一道以此标志词进行他因削弱