In much of the animal world，night is the time________for sleep－pure and simple.
| A．set aside | B．set down |
| C．set off | D．set up |
Leaders should be careful not to act beyond their __________ and do things against the law.
| A．power |
| B．violence |
| C．competition |
| D．solution |
About 270 million people in rural areas in China have no __________ to safe drinking water.
| A．entrance |
| B．access |
| C．solution |
| D．sources |
The flu is believed __________ by viruses that like to reproduce in the cells inside the human nose and throat.
| A．to be caused |
| B．to have caused |
| C．being caused |
| D．causing |
There were violent winds of 120 kilometers per hour or more in a hurricane，__________ huge waves, heavy rain and floods.
| A．causing |
| B．to cause |
| C．caused |
| D．having caused |
If city noises __________ from increasing, people __________ shout to be heard even at the dinner table in 20 years from now.
| A．are not kept; will have to |
| B．are not kept; have to |
| C．do not keep; will have to |
| D．do not keep; have to |