．People have planted a lot of trees and grass in order to ____ wind and sand in the desert．
| A．hold down | B．hold up | C．hold back | D．hold out |
President Obama held talks with Chinese President Hu Jintao in Beijing, _____ economic recovery, climate change and stopping the spread of nuclear weapons.
| A．which was discussed | B．in which they-discussed |
| C．when they discussed | D．which discussed |
The government has taken some measures to solve the shortage of electricity, but it may be some time ________ we have enough power.
| A．since | B．after | C．unless | D．before |
A small plane crashed into a hillside five miles east of the city, ________ all four people on board.
| A．killed | B．killing | C．kills | D．to kill |
At first, his teacher couldn’t' realize that Lang Lang had a ________ for music though he said he wanted to learn the piano so much.
| A．knowledge | B．present | C．gift | D．desire |
-- Perhaps Tom's not in.
-- ________. Look, the light's on.
| A．Yes, he can be at home | B．No, he mustn't go out |
| C．Yes, he must be at home | D．No, he needn't go out |