题干

近几年我国在航空航天工业上取得了长足的进步,既实现了载人的航天飞行,又实现了航天员的出舱活动.如图所示,在某次航天飞行实验活动中,飞船先沿椭圆轨道1飞行,后在远地点343千米的P处点火加速,由椭圆轨道1变成高度为343千米的圆轨道2.下列判断正确的是(  )

A:飞船在椭圆轨道1上的机械能比圆轨道2上的机械能大

B:飞船在圆轨道2上时航天员出舱前后都处于失重状态

C:飞船在此圆轨道2上运动的角速度小于同步卫星运动的角速度

D:飞船在椭圆轨道1上通过P的加速度小于沿圆轨道2运动的加速度

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B

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    Below is some advice on how to prevent cancer:

    Eat blueberries

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    Relax

    ____? Find ways to relax and you may reduce your chances of developing cancer. Purdue University researchers tracked 1,600 men over 12 years and found that half of those with high levels of worry died during the study period. Only 20 percent of the optimists died before the study were completed, while 34 percent of the extremely anxious men died of some type of cancer.____!

    Break a Sweat

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    ____

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A. Breathe clean air

B. But it has more good

C. Get away from disease

D. Do you feel stressed or worried

E. Do you have a health check regularly

F. Even a small amount of exercise can offer major cancer-fighting benefits

G. Instead of stressing about the past or future, focus on the present and have a rest