问题 多选题
2012年8月6日,美国“好奇”号火星车着陆火星表面成功,并迅速发回清晰的火星表面陨坑图象.假设“好奇”号着陆前在近火星点800千米、远火星点80000千米的椭圆轨道上履行火星探测使命.已知地球质量与火星质量之比为9:1,地球半径与火星半径之比为2:1,地球半径为6400km,地球表面重力加速度取10m/s2.由以上信息作出的下列推断中错误的是(  )

A.火星表面的重力加速度大于地球表面的重力加速度

B.火星表面的重力加速度小于地球的表面重力加速度

C.“好奇”号若要在目标轨道的近火星点开始沿绕火星的圆轨道运行,需要减速

D.“好奇”号环绕火星做圆周运动的最大速率小于地球的第一宇宙速度

答案

BCD

单项选择题
阅读理解

阅读理解

     I'm usually fairly skeptical about any research that concludes that people are either happier or

unhappier or more or less certain of themselves than they were 50 years ago. While any of these

statements might be true, they are practically impossible to prove scientifically. Still, I was struck

by a report which concluded that today's children are significantly more anxious than children in the

1950s. In fact, the analysis showed, normal children aged 9 to 17 exhibit a higher level of anxiety

today than children who were treated for mental illness 50 years ago.

     Why are America's kids so stressed? The report cites two main causes: increasing physical

isolation(隔离) brought on by high divorce rates and less involvement in community, among other

things and a growing perception that the world is a more dangerous place.

     Considering that we_can't_turn_the_clock_back,_adults can still do plenty to help the next

generation.

     At the top of the list is nurturing(培育) a better appreciation of the limits of individualism. No

child is an island. Strengthening social ties helps build communities and protect individuals against

stress.

     To help kids build stronger connections with others, you can pull the plug on TVs and computers.

Your family will thank you later. They will have more time for facetoface relationships, and they will

get more sleep.

     Limit the amount of virtual(虚拟的) violence your children are exposed to. It's not just video games

and movies; children see a lot of murder and crime on the local news.

     Keep your expectations for your children reasonable. Many highly successful people never attended

Harvard or Yale.

     Make exercise part of your daily routine. It will help you cope with your own anxieties and provide

a good model for your kids. Sometimes anxiety is unavoidable. But it doesn't have to ruin your life.

1. According to the analysis, compared with normal children today, children treated as mentally ill 50

    years ago ________.

A. probably suffered less from anxiety

B. were considered less individualistic

C. were less isolated physically

D. were probably less selfcentered

2. What does the author mean by saying "we can't turn the clock back" in the third paragraph?

A. It's impossible to forget the past.

B. The social reality children are facing cannot be forgotten.

C. It's impossible to slow down the pace of change.

D. Lessons learned from the past should not be forgotten.

3. The author thinks that the conclusions of any research about people's state of mind are ________.

A. illogical  

B. confusing

C. surprising 

D. questionable

4. Which of the following statements is TRUE according to the passage?

A. To children, anxiety is completely avoidable.

B. TV and computer play an important role in isolating children from the real world.

C. Exercise does not help to lessen children's anxiety.

D. Sometimes local news about crime and murder also affects children a little.

5. The first and most important thing parents should do to help their children is________.

A. to lower their expectations for them

B. to set a good model for them to follow

C. to get them more involved socially

D. to improve them with a safer environment