1)
A: Excuse me, do you have the time?
B: I'm sorry, I don't know. I don't have a watch.
2) 
A: No problem, thanks anyway.
A: Hey, want to go bowling this evening?
B: Sorry, I can't. I have a guitar lesson.
3) 
A: Oh, okay. Maybe another time then.
A: Why are you late? B: I'm sorry, I took the wrong bus.
A: It's alright. The movie starts at 8:30 and I have the tickets.
4)
A: Do you want to play a computer game with me?
B: I'm watching TV at the moment.
A: What are you watching?
B: I'm watching a very good movie, but it's nearly finished. We can play the computer game after the movie.