问题 选择题

若a<b<0<c<d,则以下四个结论中,正确的是(  )

A.a+b+c+d一定是正数

B.c+d-a-b可能是负数

C.d-c-a-b一定是正数

D.c-d-a-b一定是正数

答案

A、根据已知条件a<b<0<c<d,可设a=-2,b=-1,c=1,d=2,则a+b+c+d=0,是非正数,故错误;

B、由已知条件a<b<0<c<d知d+c>0,-a>-b>0,所以d+c-a-b>0,故错误;

C、由已知条件a<b<0<c<d知d-c>0,-a-b>0,所以d-c-a-b>0,即d-c-a-b一定是正数,故正确.

D、根据已知条件a<b<0<c<d,可设a=-2,b=-1,c=1,d=5,则c-d-b-a=-1,-1是负数,故错误;

故选C.

阅读理解

Life in the future will be different from life today. But what will the change be?

The population is growing fast. There will be many people in the world and most of them will live longer than people live now.

Computers will be much smaller and more useful and there will be at least one in every home. And computer studies will be one of the important subjects in school then.

People will work fewer hours than they do now and they will have more free time for sports, watching TV and travel. Traveling will be much cheaper and easier. And many more people will go to other countries for holidays.

There will be changes in our food, too. More land will be used for building new towns and houses for all the people. Then there will be less room for cows and sheep, so meat will be more expensive. Maybe no one will eat it every day. Instead they will eat more fruits and vegetables. Maybe people will be healthier.

Work in the future will be different, too. Dangerous and hard work will be done by robots. Because of this, many people will not have enough work to do. This will be a problem.

小题1:In the future there will be _______ .

A. much more fruits

B. more people 

C. fewer people

小题2:Every family will have at least one _______ .

A. robot    B. computer C. TV set

小题3:In the future people don't have to_______ .

A. work long hours 

B. work fast   

C. walk on foot

小题4:People may not eat _______ as much as they do today.

A. fruit        B. fish     C. meat

小题5:One big problem in the future is that _______ .

A. many people don't have to work

B. many people will not be able to find work

C. People have to work fast

多项选择题