第一句：I'm afraid I can't do that.

　　恐怕不行。

　　A: Can you lend me some money?

　　你能借我点钱吗？

　　B: I'm afraid I can't do that.

　　恐怕不行。

　　第二句：I'm sorry but I can't help you.

　　抱歉我不能帮你。

　　A: Could you write the thesis for me?

　　你能帮我写论文吗？

　　B: I'm sorry but I can't help you.

　　抱歉我不能帮你。

　　A: You know, I'm so busy with my part-time job recently. Would you please...

　　你知道我最近忙兼职，你能……

　　B: Sorry. But I can't.

　　对不起，我不能这么做！

　　拒绝别人的较为委婉的说法有：

　　I wish I could help you, but I can't.

　　我希望我能帮上你，可我不能。

　　I'm sorry, but I'm busy right now.

　　对不起，我现在很忙。

　　而强硬的拒绝可以说：

　　I said no and I mean it.

　　我说不行就不行。