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：考查非谓语动词和定语从句。第一空是“发现自己被一群十几岁的年轻人包围了。”用过去分词作宾语补足语表示被动，第二处用who 引导定语从句，修饰teenagers。句意：当他抬起头，他发现自己被一群年轻人包围，他们都焦虑的看着他。选B。