were to have done 和 should have done 都表示虚拟的 本应该 有什么去区别么?

题目

were to have done 和 should have done 都表示虚拟的 本应该 有什么去区别么?
You ____ part in the party on time .
A were to have taken
B were supposed to have taken
C should have taken
BC是我加的 我感觉ABC都对 你们说呢？

答案