1．--- Derek, I owe you a thank – you for all your help.
--- __________
A．If you please. B．Don’t mention it. C．That’s it. D. All right.
2. I was surprised to know that ________ two top students were caught stealing in the supermarket. Worse still, _______ third one was found fighting with others.
A. the; a B. the; the C. 不填；a D. 不填；the
3．--- Are you going to stay overnight?
--- Not __________ it’s really necessary.
A．if B．unless C．until D．since
