—I knocked but nobody answered the door. ----They _____asleep then and didn’t hear you.

—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?

_______it not been for the free ticket, I would not have gone to the cinema.

Eliza remembers everything exactly as if it _________ yesterday. 

—She looks very happy. She ______ have passed the exam.--I guess so. It’s not difficult after all.