i would have come sooner ,but i ___that you were waiting .

题目

i would have come sooner ,but i ___that you were waiting .
a.knew
b.didn't know
c.hadn't
d.don't know
写出原因!

答案

b
我应该早点来的,但是我先前不知道你在等
所以后面用过去式,因为现在已经知道你在等了,是之前不知道