问题补充：
Oh, its you, Im sorry I know you here.
A. don , are
B. didn , are
C. didn ,were
D. don , were
答案：
A. don , are
B. didn , are
(答案→)C. didn ,were
D. don , were
解析：时态的呼应,有一些从句，特别是在宾语从句中，谓语动词的时态经常受主句谓语动词时态的影响。说话人必须使之一致，如：I did not know you were here。本来you were here 该用you are here。但由于受did not know的影响，就要用you were here。这种现象就叫时态的呼应，如下列句子：He told us that he would go abroad.他告诉我们他要出国。
