i'm sorry ___ you about it before.

问题描述:

i'm sorry ___ you about it before.
a.not to tell
b.not to have told
为什么不选a?

b.not to have told
have done 意思是本来应该做,却没有做
我很抱歉,我本来应该提前告诉你,却没有.
祝好!