问题补充：
— I to your birthday party last Sunday.
— Unfortunately, you were out on business.
A. had come
B. came
C. would come
D. would have come
答案：
A. had come
B. came
C. would come
(答案→)D. would have come
解析：根据对话情景可知，答句Unfortunately, you were out on business.（不幸的是你出差了）实际上是上一句暗示的条件。从答句所给的特定的动词时态（一般过去时）来看，上句所说内容是对过去情况的假设，故暗示的条件句应为If I hadn’t been out on business，由此可见，选项部分为主句的谓语动词，表示与过去事实相反，应选用would have come。
