根据所给情景，从A、B、C三个选项中选出最佳选项。

1. — Can I take this seat?

    — _______. It's for our teacher, Mr Li. [ ]

A. Of course

B. You'd better not

C. Yes, please

2. — You speak English well.

    — _______. [ ]

A. Don't say so

B. Just so-so

C. Thank you

3. — There's going to be an exciting basketball match in our school.

    — _______ I can't wait. [ ]

A. It's boring.

B. What a pity!

C. That's great.

4. — I have to make a speech at a meeting. I feel nervous about it.

    — _______. I'm sure you can do it well. [ ]

A. Take it easy

B. Don't be so sad

C. That's all right

5. — What do you think of the math problem?

    — _______. All of us can work it out. [ ]

A. It's a piece of cake

B. It's difficult

C. I hope so