You didn’t let me drive. If we ______ in turn, you ______ so tired.

— Is John coming by train ? — He should, but he ______ not. He likes driving his car. 

—The research on the new bird flu virus vaccine is challenging and demanding. Who do you think can do the job?—____ my students have a try?

— Linda hasn’t shown up yet.— It’s strange. She ____.

--Excuse me, you are supposed to hand in your design now.--I’m sorry, my computer broke down, or I ________ it last night.