问题
选择题
I _____ his telephone number. Had I known it, I would have rung him up.
A．don’t known
B．didn’t know
C．hadn’t known
D．haven’t known
答案
答案：B
题目分析:考查动词时态。后句的虚拟语气是对过去的虚拟，由此可知此处是讲述过去的事实，故用一般过去时，答案选B。句意：我不知道他的电话号码。如果我知道的话，我就会给他打电话了。