My father warned me going to the West Coast because it was crowded with tourists.A. onB.

网友回答

A. on
B. for
C. of
(答案→)D. against
解析：句意：我的父亲警告我不要去西部海岸，因为那里有许多旅行者。warn sb of sth警告某人做某事；warn sb against sth警告某人不要做某事；根据句意故选D。