I would love to your birthday party last night but I had to attend an important meeting.

问题补充：

I would love to your birthday party last night, but I had to attend an important meeting.

A. to go

B. to have gone

C. going

D. having gone

答案：

A. to go

(答案→)B. to have gone

C. going

D. having gone

解析：would love接不定式，would love to have done表示“本来愿意做某事而实际上没有这样做”。