句：I'm sorry.

对不起。

A: Why are you late again?

你为什么又迟到了？

B: I'm sorry. I missed the bus.

对不起，我错过车了。

A: Do you think I will believe such a story agian?

你以为我还会相信这样的鬼话吗？

B: Well...er, to be frank, I got up late.

嗯···呃，坦白说，我起床晚了。

第二句：This is really embarrassing.

真是不好意思。

A: I shouldn't have done such a thing. This is really embarrassing.

我真不该做那样的事，真是不好意思。

B: It doesn't matter. Let's drop the subject.

没关系，我们别谈这个话题了。

其他表达法：

It's all my fault.

都是我的错。

Please accept my apologies.

请接受我的道歉。

Excuse me for taking your time.

请原谅我耽误你的时间了。

Sorry to interrupt you.

很抱歉打扰您。