Much to my I am unable to accept your invitation.A. faultB. failureCpleasureD. regret

问题补充：

Much to my ,I am unable to accept your invitation.

A. fault

B. failure

Cpleasure

D. regret

答案：

A. fault

B. failure

C. pleasure

(答案→)D. regret

解析：考察名词词义辨析。A过错；B失败；C快乐；D遗憾；句意：让我遗憾的是，我不能接受你的邀请。根据句意说明D正确。