how to refute D
negate D)..."Airlines are NOT less reluctant to report mechanical problems than they previously were" that means they are more reluctant to report the problems. then the conclusion of the author is right. he can logicially assume that although the airlines are less reluctant the rate of problems increased. so the only fair conclusion is that the new measure are responsible for the increase.
If your mind can conceive it and your heart can believe it, have faith that you can achieve it.