—Why didn't you answer my phone when I phoned you at about 11 p. m. yesterday?
—I ___________and failed to hear the phone.
| A．might have slept | B．must be sleeping |
| C．might be sleeping | D．must have been sleeping |
The poisonous atmosphere will surely ______a lot of people.
| A．effect | B．impress | C．cause | D．affect |
Before the first nonstop flight made in 1949,it______necessary for all planes to land for refueling.
| A．would be | B．has been | C．had been | D．would have been |
—Have you found anything wrong with your computer?
—Yes,and I was about to give it up when an idea ______to me that it may be struck by some kind of virus.
| A．occurred | B．happened | C．took place | D．turned |
We______our breakfast when an old man came to the door.
| A．just have had | B．have just had | C．just had | D．had just had |
Although there is a difference in spelling,pronunciation between American English and British English,both of the countries have much to________
| A．share | B．communicate | C．spare | D．improve |