When he looked up，he suddenly found himself by a group of teenagers， looked at him anxiously.
A. to be surrounded；which
B. surrounded；who
C. be surrounded；who
D. having been surrounded；which
网友回答
A. to be surrounded；which
(答案→)B. surrounded；who
C. be surrounded；who
D. having been surrounded；which
解析：考查分词用法和定语从句。Him与surround构成被动关系，所以使用过去分词。第二空who指代先行词a group of teenagers在句中做主语。句意：当他抬头看的时候，突然发现自己被一群年轻人包围着，这群年轻人焦急地看着他。