【正确答案】 D

【答案解析】[解析] 画线词mock为动词，意为“取笑；嘲笑”。A项smile at意为“笑(某人或某事)”，例：what are you smiling at?你在笑什么?B项look down on意为“看不起”，例：Small boys usually look down on little girls and refuse to play with them.小男孩常常看不起小女孩，因此不愿意跟她们玩。C项belittle意为“贬低；低估”，例：Don"t belittle what he has achieved.不要贬低他所取得的。D项laugh at意为“取笑；嘲笑”，例：It is unkind to laugh at the person who is in trouble.嘲笑有困难的人是不友善的。故选D。