“Why has it been difficult to find buried treasure on Cocos Island?” is a more useful research question than “Why did whalers stop visiting Cocos island?” because —
A. The question about difficulties is general.
B. The question about whalers can be answered with only one fact.
C. Answering the question about difficulties would require interviewing historians in Costa Rica.
D. Answering the question about whalers would require special resources not found in most libraries