Gun control is a subject American 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：考查定语从句，先行词是a subjet，定语从句argue后面缺少介词about+宾语，用about which引导定语从句，句意：枪支的控制是美国人争论了很长时间的话题。选C。