But for their common efforts, they achieved so much in their research.
| A．could have |
| B．will not have |
| C．could not have |
| D．have not |
I don’t mind her criticizing me,but___is how she does it that I object to.
| A．it | B．that |
| C．this | D．which |
Experts have been warning___of the health risks caused by passive smoking.
| A．at a time | B．at one time |
| C．for some time | D．for the time |
After graduation she reached a point in her careershe needed to decide what to do.
| A． | that | B． | what |
| C． | which | D． | where |
—I have got a headache.
—No wonder.You___in front of that computer too long.
| A．work | B．are working |
| C．have been working | D．worked |
The melon the Smiths served at dinner would have tastedif it had been put in the fridge for a little while.
| A． | good | B． | better |
| C． | best | D． | well |