问题补充：
Peter went to a concert his favourite band played and sang.
A. which
B. for which
C. at which
D. in which
答案：
A. which
B. for which
(答案→)C. at which
D. in which
解析：这是which引导的定语从句，在音乐会上这种虚的地方也用表地点的关系词，故用at which句意：皮特去听音乐会了，在这次音乐会上他的最喜欢的乐队在音乐会上演奏和歌唱。故选C。
