Gun control is a subject Americans have argued for a long time.
A. of which
Bwith which
Cabout which
D. into which
网友回答
A. of which
B. with which
(答案→)C. about which
D. into which
解析：C考察定语从句。先行词是gun control指物，关系词在从句做介词的宾语，介词前置，介词和从句动词的搭配argue about，故C正确。