【题目】The leaders of the country are discussing the problem, ________ they have argued for more than an hour.
A. about which B. against whom
C. for which D. to which
在线课程【答案】A
【解析】
试题分析：考查关系词。句意：国家首脑正在讨论问题，他们已经讨论了超过一个小时了。Argue about sth，争论....，缺少介词，非限制性定语从句用which连接，故选A项。