Although everything seems to have been taken into consideration, ________ accident can happen when the astronauts walk in ________ space.
| A．/; the | B．an; the | C．the; the | D．an; / |
Look! The ground is wet. It must have rained last night, ________？
| A．hasn't it | B．hadn't it |
| C．mustn't it | D．didn't it |
—Did you tell her the bad news?
—Yes, but I'd rather ________.
| A．didn't | B．not |
| C．not have | D．hadn't |
He is only too ready to help others, seldom, ________， refusing them when they turn to him.
| A．if never | B．if ever |
| C．if not | D．if anything |
A recent study has found that the number of smokers ________ sharply over the past five years.
| A．is increasing |
| B．are increasing |
| C．has been increasing |
| D．have been increasing |
How close parents are to their children ________ a strong influence on the development of the children's characters.
| A．having | B．had |
| C．has | D．have |