Answer choice A??

@erojas the conclusion of the argument is "the airlines should rethink their training approach to reducing commercial crashes." Why? Studies have shown that pilot error contributes to two-thirds of all such crashes. To address the problem, the airlines have upgraded their training programs by increasing the hours of classroom instruction and emphasizing communication skills in the cockpit. However, the passage states that it is unrealistic to expect that these measures alone will compensate for pilots' lack of actual flying time. (A) definitely seems to strengthen the argument by point out that training programs can impact pilot errors (i.e. so rethinking the training program can have an impact). But notice that when you negate (A) it also strengthens the argument that "the airlines should rethink their training approach to reducing commercial crashes" (i.e. because training programs cannot necessarily eliminate pilot errors). Hope that helps! Please let us know if you have any other questions.