Gun control is the subject Americans have argued for a long time.
A. which
B. with which
C. about which
D. of which
网友回答
A. which
B. with which
(答案→)C. about which
D. of which
解析：考查定语从句。argue about 争论什么，先行词为the subject，故用about which，句意：控制枪支是一个美国人争论了很长一段时间的话题。