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?

• AThe major causes of delays at the nation's busiest airports are bad weather and overtaxed air traffic control equipment.  
• BSince airline deregulation began, the number of airplanes in operation has increased by 25 percent.  
• COver 60 percent of the takeoff and landing slots at the nation's busiest airports are reserved for commercial airlines.  
• DAfter a small Midwestern airport doubled its allocation of takeoff and landing slots, the number of delays that were reported decreased by 50 percent.  
• ESince deregulation the average length of delay at the nation's busiest airports has doubled.