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 |
She is very _______ about this topic, so we’d better not discuss it in front of her.
| A．confident | B．crazy | C．sensitive | D．humorous |
I suggested that they set off early to avoid (避开) the traffic jam, _______ no one responded.
| A．on which | B．to which | C．about which | D．for which |
Nowadays, use____________of certain waste materials to protect the environment.
| A．is making | B．will make | C．is being made | D．will be made |
He has been heavily _______ to the bank since he bought that big house in Beijing.
| A．in debt | B．in peace | C．in danger | D．in cash |
---Tom, must you have the light______ all night? It’s really a waste.
---Sorry, I won’t do it again.
| A．burning | B．burned | C．to burn | D．to be burned |