请帮忙解答一道英语单选题.

问题描述:

请帮忙解答一道英语单选题.
1.Why didn't you come to the party yesterday I__,but an unexpected visitors came to see me A.did B.would C.had D.was

B
题意是:昨天你为什么没有来聚会?
我本来想去的,但是有一个不速之客来看我.
回答用的是虚拟语气,所以用would.