（还可以说：I can't tell you how sorry I am./
I really feel bad about it./
I'm so/awfully/terribly sorry. ）
（还可以说：I beg your pardon./
Please forgive me.）
That's all right.
（还可以说：It doesn't matter./
Apology is really quite unnecessary.
I demand an apology.
Why should I apologize?
Please excuse me for being late.
Please excuse the offence this time, I will not do it again.
I'm terribly sorry to have caused you so much trouble.
A: Julia, I apologize to you for what I have done. Please forgive me.
B: I've already forgiven you. Actually, I also owe you an apology. I was so rude to you that day.
A: It doesn't matter. I know that people are easy to get mad when they are tired.
B: Thanks for your understanding.