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 |
School children must be taught how to deal with dangerous ______ .
| A．states | B．conditions |
| C．situations | D．positions |
He has been to general manager because of his excellent work in the company.
| A．proposed | B．produced |
| C．promoted | D．programmed |
Despite some difficulties，China has achieved a lot in the past year ______ .
| A．off balance | B．in the balance |
| C．on balance | D．on the balance |
After you have used the dictionary, please put it back ______ it belongs.
| A．to whom | B．to which |
| C．what | D．where |
A wonderful idea suddenly occurred to me ______ I would turn to the reference book to finish my homework.
| A．that | B．if |
| C．when | D．which |