Complete the dialogues with one word in each gap.

1. A: I can't find my book! B: I've got it! Sorry about that. A: That's all right. 2. A: Oops! I'm so sorry! B: It's OK. A: Are you sure? B: Yes, I'm fine. 3. A: These aren't my keys. B: Sorry, my mistake. Here you are. A: No problem.