Complete the sentences with can or could.
Tom: Really? That sounds horrible!
Dan: (Can,Could you dive, Tom?
Tom: Yes, a little. You (can,Could) dive very well, Dan. When did you learn to do that?
Dan: I (can,could) dive when I was six years old.
Tom: Really? I (can,Could) swim when I was young, but I only learnt to dive last week!