He had to pause from time to time to wipe the sweat from his forehead, because the air—conditioning system ______________.
WheneverIwasintrouble,hewoulddowhathecould________me.
According a recent survey, if the factory closes, a lot of people _______ their jobs.
________ hard, and you will pass the final exam.
The past 30 years has ______ the great changes that have taken place in China.
– I’m sorry for what I said. -- Forget it, I can’t remember _________.