I am terribly sorry to tell you that_________,and I am writing this letter to show my deep regret.Please accept my sincere apology with gratitude.I hope you will understand my situation and excuse me for___________.
The reason why__________is that__________.Under that circumstance,____________.Therefore,it was not my power to___________.
If possible,I would like to suggest that___________.I shall be obliged if you will kindly write and tell me___________.I am looking forward to seeing you again.
I am writing you this letter to apologize for my failing to hand in the paper on time.I am very sorry for the inconvenience brought by my delay.Please accept my sincere apology with gratitude.
The reason for my delay was the I was knocked down by a cold.Moreover,I had a fever and was too weak to write a single word.Therefore,it's not in my power to finish the paper on time.I hope you could understand me and excuse me for my delay.
I will do my utmost to finish my paper and hand it in as soon as possible.In my opinion,the importance of punctuality you cannot be emphasized too much,so I assure you that I will hand in my homework on time from now on.