He will you next week if he is free.
A. drop in
B. drop in at
C. drop in on
D. call at
网友回答
A. drop in
B. drop in at
(答案→)C. drop in on
D. call at
解析：考查动词短语辨析。Drop in随便拜访；该短语后面不能直接加宾语，要接介词；drop in on sb拜访某人；drop in at some place参观某地；句意：如果下个星期他有空，他会去看你的。故C正确。