— Come and join us, Ben!
— I’m afraid I can’t. I’m too busy now. If I time, I would certainly go.
A . had B . will have C . have had D . have
A
【详解】考查虚拟语气。句意: —— 来加入我们吧,本 !—— 恐怕不行。我现在太忙了。如果我有时间,我一定去。结合空后 “I would certainly go.” 可知,此处使用了 if 条件句的虚拟语气,表示与现在事实相反,其结构为: If+ 主语 + 动词的过去式 (be 动词用 were)+ 其它,主语 +would/could…+ 动词原形 + 其它;由此可知,空处需用动词的一般过去时。故选 A 。