.They thought about it for a long time, but still couldn’t ________ a solution.
The chemistry teacher required the students _______ more attention _______ the lab clean.
If you are worried about the problem,you should do something it.
We’ve talked a lot _______ cars. What about trains?
We’re all going to the games.Why don’t you come ?
It was very kind of her. She insisted _______ her car to us.