I regret you that we are unable to offer you a job.A. informingB. having informedC. to i

问题补充：

I regret you that we are unable to offer you a job.

A. informing

B. having informed

C. to inform

D. to informing

答案：

A. informing

B. having informed

(答案→)C. to inform

D. to informing

解析：regret to say/inform/tell表示很遗憾……，近似于Im sorry to say. regret doing表示对发生的事后悔，懊悔或惋惜。