We _____ three thousand new words by the end of last year.
–Why do you like climbing mountains? --Because they are there and climbing is _____thing I have ever done.
It is said the cost of medical care today is ten times as ____ as it was ten years ago.
– Look at these factories. I hate them. They____ many rivers here. --Yes. Something ______ to stop the pollution.
--David will never ____ though he fails again and again. --_______. So I believe both of you will succeed one day.
–Look at that red bike, it _____ belong to you. I have seen you ride it. --But it ____ be mine. Mine is broken. I am having it repaired.