(2009·陕西)Gun control is a subject Americans have argued for a long time.
A. of which
B. with which
C. about which
D. into which
网友回答
A. of which
B. with which
(答案→)C. about which
D. into which
解析：先行词为subject，将先行词还原到定语从句中：Americans have argued about the subject for a long time。由此可以看出被还原部分为about the subject，这样可以确定所选的介词为about。