Dear John, Thank you for your invitation to dinner at your home tomorrow evening. 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. I feel terrible sorry for missing the chance of such a happy get-together, and I hope that that all of you enjoy a good time. Is it possible for you and me to have a private meeting afterward ? If so, please don’t hesitate to drop me. I do long for a pleasant chat with you. Please allow me to say sorry again. Look forward to your reply.