题目选项分析

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?

【选项】Since deregulation the average length of delay at the nation's busiest airports has doubled.