[greymule]

I think you may be right, Shipwreck. I had a problem with question #45, too, and at our rules meeting brought up the fact that an unreported substitute is not necessarily an illegal player. In fact, 4-6-B-2 clearly implies that the unreported substitute might not be an illegal player. In the hurried atmosphere of the meeting, I accepted the explanation they gave me. But apparently, only if the unreported substitute was an illegal player would he be called out.

Unless some other poster can explain why "a" is indeed correct, I think ASA wrongly equated "unreported substitute" with "illegal player" and produced yet another faulty question.