根据对话内容，从方框中选择能填入空白处的最佳选项。

A: I have a problem, Amy. I'm very worried.

B: Sorry to hear that.   1

A: My pen friend in the USA hasn't replied to my last three e-mails. I don't think she will write to me any more.

B:  2   Maybe she's busy these days.

A: Perhaps you're right.   3

B: Why don't you send her an e-card and tell her you miss her very much?

A: 4   Thanks for giving me the suggestion, Amy.

B: 5