In communication, a smile is usually _____ strong sign of a friendly and ____ open attitude.
| A．the; / | B．a ; an | C．a ; / | D．the; an |
—Could we go and visit the Summer Palace?
—Yes，________.This should be on our list of things to do in Beijing.
| A．a pleasure | B．it depends |
| C．don't mention it | D．by all means |
It's OK to________an electrical appliance on so long as you are using it.
| A．leave | B．make |
| C．turn | D．open |
It________heavily for 2 weeks and the farmers were very worried.
| A．has been raining | B．had been raining |
| C．has rained | D．had been rained |
You cannot tell________looking at someone whether or not he has HIV.
| A．without | B．by |
| C．for | D．with |
The days are gone________you can breathe fresh，unpolluted air or drink clean, unpolluted water in the countryside.
| A．when | B．that |
| C．where | D．which |