Dear David:，
I am afraid that you will think me unpardonably negligent in not having answered your letter dated 7, December sooner, but when I have told you the reason, I trust you will be convinced that the neglect was excusable. When your letter arrived, I was just in Hong Kong. As my family could not forward it to me during my absence, it has been, therefore, lying on my desk until the moment when I took it up. Now the first thing I have to hasten to do is to write to you these few lines to express my deep regret.
yours，
Sara
Dear Mr. Smith,
I am indeed very sorry that I missed the examination on International Business English Writing you gave last Friday. I feel awful about it and want you to know what happened that day.
I suddenly fell sick early that morning and my parents had to send me to the hospital. Please find enclosed a copy of the medical bill.
I sincerely hope you can understand my situation and accept my apology. I would appreciate your allowing me to take a make-up examination. I will come to your office during your office hour on Monday to discuss this possibility with you.
Once again, I apologize for any inconvenience caused.
Sincerely yours,
xxx
Dearxxxxx,
I am writing this letter to express my apology that xxxxxxxxxxxxxx. I feel terribly sorry about this.
Once again, I am very sorry for any inconvenience caused. I will be really appreciated if you can accept my apologies and understand my situation. Yours Sincerely xxxxxxxxx
亲爱的xxxxx，(对方姓名)
我写这封信以表达我的道歉 xxxxxxxxxxxxxx(道歉原因)。
对此我深感抱歉。
我再次对给您造成的任何不便深感歉意，希望您能理解我的处境并接受我的道歉。
谨启
xxxxxxxxx(自己姓名)
Dear Prof. Patent,
I am very sorry to inform you that I did not manage to complete the book report you assigned last week, due to a sudden illness falling upon me a few days ago.
For the past few days I have been in hospital with a continuous fever, which has thus prevented me from any academic activity. I hereby submit the doctor's note. I would be very much obliged if you could grant me another week for the task, as my health is turning better.
Hope you can understand my situation and accept my apology.
Yours faithfully, Li Ming
译文
尊敬的.Patent教授：
我非常遗憾地告知您我没有完成您上周布置的读书报告，因为几天前我突然生病了。
过去的几天中我一直持续高烧，住在医院，因此无法进行任何学术活动。随信是医生的诊断书。
如果您能再给一周时间来完成它我将感激不尽，因为现在我的身体正在好转。希望您能理解我的处境并接受我的道歉。
您真诚的，李明