题干

核电站中采用反应堆使重核裂变,将释放出的巨大能量转换成电能.反应堆中一种可能的核反应方程式是 92235  U+ 01 n→ 60143 Nd+ 4090 Zr+x+y,设U核质量为m1,中子质量为m2,Nd核质量为m3,Zr核质量为 m4,x质量为 m5,y质量为 m6,那么,在所给的核反应中(   )

A:x 可能是3 11 H,y 可能是11﹣ 10 e

B:x 可能是3 01 n,y 可能是8﹣ 10 e

C:释放的核能为(m1+m2﹣m3﹣m4﹣m5﹣m6)c2

D:释放的核能为(m3+m4+m5+m6﹣m1﹣m2)c2

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答案(点此获取答案解析)

B,C

同类题4

阅读下面短文,根据其内容,从方框中选择适当的单词填在标有题号的空白处,使语意通顺、完整.(每空一词,切不可重复使用)

moving    direction    fall      hands      where    protect     yourself

against    as        up     possible     easily     them  thing   ground

 What should you do if you are in a crowd(人群)? The first and most important ____   is to make yourself clear where you are and where the exits are. No matter ____  you are, make sure you always know how to get out and to be safe.

 Make yourself know the type of  ____  you are standing on. Wet or uneven(不平坦的)ground can cause you to ____  down in a crowd of moving people.

 If you find ____   in the middle of a moving crowd, you must be careful. Do not walk ____  the moving direction and do not stop or sit down, because you could get trampled (踩踏)  ____ Instead, move in the same ____  of the crowd. Keep your____  up by your chest(胸部)to protect your chest. If you fall down, get up quickly, If you can't get  ____  , ask someone to pull you back up. If you have kids, lift  ____  up.

 If you fall and cannot get up, keep on  ____   in the same direction of the crowd. If that is not  ____   , then cover your head with your arms.

 Try to get away from hard things in a crowd. If you're pushed against them, ____   a result, you may be hurt badly.

 We should learn to ____  ourselves. Stay away from the crowd.

Remember: Whatever you do, safety is first!