----Why didn't you go to Mike's birthday party last night?-----well,I ___,but I forget it.

问题描述:

----Why didn't you go to Mike's birthday party last night?-----well,I ___,but I forget it.
A,should B.should have

B
本应该是虚拟语气吗?为啥要have?should have是本应该而没有做的意思