1、因未能践约赴宴致歉 Unable to keep one''s promise
Dear Miss Nancy，
Much to my regret I was unable to keep my promise to attend your birthday party last Saturday，owing to the fact that my little son was suddenly taken ill early that day.
Hoping to see you soon.
2、因迟复来信致歉 Because of answering one''s letter late
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.
I enjoyed many pleasant sights during my trip. I shall be pleased to give you an account to of them when I see you next.
3、因未能及时还书致歉 Unable to return borrowed book on time
Excuse me for my long delaying in returning to you your Robinson Crusoe which I read through with great interest. I had finished reading the book and was about to return it when my cousin came to see me. Never having seen the book， She was so interested in it that I had to retain it longer. However，I hope that in view of the additional delight thus afforded by your book， you will overlook my negligence in not returning it sooner.
Thanking you again for the loan.
4、因遗失借书致歉 Because of losing a borrowed book
I am terribly sorry to tell you that I have lost the valuable book you were so kind to lend me last week. I read it everyday and intended to finish it next month. Last night when I came to my room，it was nowhere to be found. I will try to recover it as soon as possible. If I fail to find it，I will get a new book for you.
But I am afraid it can never take the place of the old one. Old books are like old friends. Once lost，they can never be replaced. They are connected with cherished associations which the new ones can never have. And for this irrecoverable loss，I am to blame. I was so careless with my things. This is a warning to me to be more careful in the future.