______ a good insulator(绝缘体) , rubber is often used in cables.
| A．Having been | B．To be | C．Be | D．Being |
Hardly had we entered the room________ it began to rain.
| A．while |
| B．as |
| C．then |
| D．when |
—When did the computer crash?
—This morning，while I ________ the reading materials downloaded from some websites.
【选项
| A．have sorted |
| B．was sorting |
| C．am sorting |
| D．had sorted |
I was wandering through the street ________a beggar stopped me for some money.
| A．when |
| B．while |
| C．unless |
| D．since |
You got second and Tim first in the race! How did Tim beat you?
——________ ? Maybe he is just a lucky dog!
| A．What for | B．Who knows |
| C．So what | D．Guess what |
Laura’s knee pain ______ from such activities as running, hiking and horse riding.
| A．puts her up | B．holds her back |
| C．takes her off | D．gives her away |