Explanation: The Crusades were initially very successful in conquering Jerusalem and the Levant, but determined Muslim resistance pushed the Christians out, and the Fourth Crusade conquered Constantinople instead of fighting against the armies of Islam. Choice (A) is historically untrue, so eliminate it. Eliminate (B) because the Crusades helped build Mediterranean trade routes, and this choice states the opposite. Eliminate (D) because the Byzantines were decisively beaten by the Turks, not the other way around. The correct answer is (C).