【题目】The murder reminded us of gun control—a subject people have argued for a long time.
A. of whom B. about whom
C. about which D. of which
在线课程【答案】C
【解析】句意：这起谋杀事件使我们想起了枪支管制——一个人们争议已久的话题。分析句子结构可知，空处引导定语从句，修饰先行词a subject；argue about sth.意为“争论有关……”，是固定搭配，故答案选C项。