a) A: Come and play volleyball, ...

B: I'm sorry. I don't think I can.

A: That's too bad. Why not?

B: Well, I should visit my grandfather.

A: Can you play on the weekend?

B: Yes, I can.

A: All right. See you on Saturday afternoon.

B: Ok. Bye.

A: Bye.

b) A: Would you like to play chess?

B: I'm sorry. I don't think I can.

A: That's too bad. Why not?

B: Well, I ought to help my Dad.

A: Can you play on Wednesday night?

B: Yes, I can.

A: All right. See you at six o'clock.

B: Ok. Bye.

A: Bye.

c) A: Let's play badminton!

B: I'm sorry. I don't think I can.

A: That's too bad. Why not?

B: Well, I must go to the dentist. 

A: Can you play on Sunday morning.

B: Yes, I can.

A: All right. See you at ten o'clock. 

B: Ok. Bye.

A: Bye.