【题目】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

【答案】B
【解析】考查非谓语动词和定语从句。“发现自己被一群十几岁的孩子包围了”。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。