Answer (A) is incorrect because it is too strong of a statement. The first sentence states that flexible work schedules "do no typically" increase manager's job satisfaction, possible because they already had flexible schedules. Answer (A) states that flexible schedules will be an "effective means of increasing" job satisfaction and for managers who didn't have flexible schedules before. But, this is much stronger than the sentence in the argument. We only know that flexible schedules didn't change much for managers and that was hypothesized to be because they already had them. So, it is an assumption to say that managers who don't have flexible schedules would be more satisfied with them. Maybe managers don't like flexible schedules, we really don't know from the information provided.
Answer (E) is correct because it follows from the argument. We are told that manager's job satisfaction doesn't improve when given flexible schedules but that non managerial employees report higher satisfaction with flexible schedules. So, we know that the manager's experience does not translate to all employees. Answer (E) reflects this by saying that you can't judge the benefits flexible schedules by looking at managers.