非常抱歉，我不能接受你的邀请 。
2、Much to my regret,I refused to accept your kind invitation.
（当时）拒绝您的盛情邀请，深感后悔 。
3、Unfortunately, it is much to my regret that I cannot join you and your family, because I will be fully occupied then for an important exam coming the day after tomorrow.
可是，我非常遗憾地告诉你我无法赴约，因为我将忙于准备后天的一门重要 考试 。
文章插图