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：考查非谓语动词及定语从句。第一空考查过去分词作宾语补足语，表示“发现自己被包围”；who引导非限定性定语从句，指代先行词teenagers。故选B。