题目内容：

Mr.Hopkins didn't know___.A.whom they were waiting B.whom they were waiting for并说明

优质解答

Mr.Hopkins didn't know （B.whom they were waiting for）.
霍普金斯先生不知道他们在等谁.
wait（等待）是不及物动词,等待某人要说成“wait for sb”,要有介词的帮助才能接宾语.所以A项是不完整的,要选择B.