79. Before there goes the bell for class, our math teacher took out a piece of and wrote his problems on the blackboard.
I _____ while watching the movie 2012 last night. Unluckily, my roommate woke me up.
_____ that air conditioners cause so much pollution, I would never have bought one.
Jumping out of ____ airplane at ten thousand feet is quite ____ exciting experience.
–Why didn’t you give a hand to the boy? -- I ______ , but he struggled to his feet before I tried to.
The moment _____ John will never forget is ______ Mr. Smith gave him a lot of valuable advice on how to improve his writing.