_______, there would be no air around the earth

1. A.
   There were no gravity
2. B.
   There was not any gravity
3. C.
   Were there no gravity
4. D.
   was there no gravity

根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。
This report presents details of home computers used by a random sample (随机抽样) of young people. It is a common idea that teenagers today know about computers and know how to use them in all aspects of their lives. We decided to try to find out whether that was true.
 【小题1】  All the teenagers we chose said they had computers at home. We asked them how much time they spent on their computers in an average week, but we were most interested in what they used their computers for. The average time spent on a computer in a week was about 12 hours, with the highest user averaging 32 hours and the lowest user only 5 hours.   【小题2】   【小题3】  Fourteen teenagers told us they did some word processing at home, but not very much. Only 2 of them said that computers helped them with their studies, while 8 of them told us they kept addresses and telephone numbers on their computers or used them as diaries. Only 3 of them said they were learning to program computers, and nobody looked up information (other than their address lists).   【小题4】 
The results indicate quite clearly that computers are seen by most young people as little more than game machines.   【小题5】  It seems to us that, although computers are common in the homes of teenagers, they have not yet become useful tools in everyday life.

________ , we had to go home.

-- Isn’t that Ann’s husband over there?

-- No, it ________ be him. I’m sure he doesn’t wear glasses.

My father worked day and night. Otherwise, there ________ no one to support the family.

A．would be          B．must be           C．would have been    D．must have been