Conversation using Could
A: I really enjoy the way you play the piano!
B: Thanks. I've been practicing for many years. Can you play a musical instrument?
A: No. When I was a child, I could (a) play a little, but not now. Could (b) you teach me?
A: If I had the time, I could (d) teach you, but now I'm too busy at work. Maybe in the future
I'll have more time.
B: I have an idea! I could (c) help you with your math homework, and you could (c) teach me the piano.
A: That's a good idea. It could (d) work!