第4题: [单项选择]The manager is well aware of a few other problems ______ he knows we have had with the customers in the past five years. A. which B. those C. what D. whichever 参考答案:A 答案解析:超高级问题 空格前后有两对“主语+动词”,所以空格内应填入连词。he knows是插入语。B选项不能做连词,what和whichever在前面没有先行词的时候使用。正确答案是which,做关系代词,在