答案是A，我怎么感觉B才是正确

斯巴达

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.  是由其它因素引起的，而不是人为因素  感觉答案不是很好  
(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.