— Come and join us Jimmy!— I’m sorry but I’m really busy now. If I time I would certai

问题补充：

— Come and join us, Jimmy!

— I’m sorry, but I’m really busy now. If I time, I would certainly go.

A. have

B. have had

C. had

D. will have

答案：

A. have

B. have had

(答案→)C. had

D. will have

解析：if 引导的条件状语从句，从句用过去时，主句要用过去将来时。