Many people who fly at least occasionally have come down with a cold or the flu shortly after disembarking. Is the air in airborne commercial jets 1 The Association of Flight Attendants (AFA), 2 which 42,000 flight attendants with 27 airlines are represented, evidently thinks so. The organization claims that the incidence of air-quality-related diseases has 3 among its members and demands that prompt actions be 4 to improve the conditions in the airplane cabin.A study the AFA 5 in 1997 uncovered about 1,000 self-reported incidents of headaches, dizziness and memory loss 6 flight attendants and passengers. Some flight attendants were too ill to 7 their safety duties, while others have been permanently disabled.Because of airlines" efforts to 8 their expenses, cabin-air filters are not cleaned 9 . The complaints of flight attendants do not always give 10 to correct maintenance. Airlines turned to recycled air, 11 that they would reduce some of their costs. They are not required to put filters in. Airlines are 12 great pressure to get their flights out 13 . So they do not pay as much attention to systems that are not as 14 to flight schedule and safety.Recent research findings emphasize the concern that filters can 15 engine chemicals into the cabin air. This may not happen 16 every flight, but it is a persistent problem.In a study published in October 1998 an investigation was made 17 complaints of crew members 18 air quality and health. More than half of the 200 subjects reported health problems they 19 to cabin air. It was concluded that these health problems were consistent with 20 harmful gases and substances.

A. hope
B. attention
C. rise
D. chance