A：Where were you last night, at exactly nine twenty PM?
B：nine twenty pm,I couldn't say.I cann't remember.
A：Are you sure you cann't remember?
B：I've absolutely certain.
A：Were you in or out?Can you remember that?
B：I'm not quite positive.I think I went out at about half pass nine.
A：Did you see anyone come into the block flats?
B：No, I didn't.
A：Sure?
B：Quite sure.