—I stayed at a hotel while in New York.
—Oh, did you? You ________ with Barbara.
| A．could have stayed | B．could stay |
| C．would stay | D．must have stayed |
An increased concentration of carbon dioxide and certain other gases in the Earth’s atmosphere ______ global warming.
| A．contributing to | B．contribute to |
| C．contributes to | D．to contribute to |
Sometimes I act as a listening ear for fellow students ______ what is bothering them.
| A．to talk over | B．talked about |
| C．talk about | D．having talked over |
It was not until the end of the trip ______ I realized what a good feeling it was to have helped someone in trouble.
| A．as | B．that | C．where | D．when |
We would rather our daughter ____at home with us, but it is her choice, and she is not a child any longer.
| A．would stay | B．has stayed |
| C．stayed | D．stay |
In the time of social reform, people’s state of mind tends to keep _____ with the rapid change of society.
| A．contact | B．progress | C．touch | D．pace |