I regret ____you that we are unable to offer you employment

1. A.
   informing
2. B.
   having informed
3. C.
   to inform
4. D.
   to have informed

I regret _____ hard at school, or I would have succeeded in passing the exam.

A. not to work                            B. having not worked

C. to have not worked                      D. not having worked

We regret to inform you that there are no tickets ______ for Friday's performance.

A．available B．usefulC．convenientD．affordable

I regret to say your performance didn’t reach the relevant requirements, ______you cannot be accepted by the company.?

A. in a word?       B. in other words?

C. after all?        D. on the other hand

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

A. informing　B. having informed  C. to inform　D. to informing