问题 不定项选择

若原子的某内层电子被电离形成空位,其它层的电子跃迁到该空位上时,会将多余的能量以电磁辐射的形式释放出来,此电磁辐射就是原子的特征X射线。内层空位的产生有多种机制,其中的一种称为内转换,即原子中处于激发态的核跃迁回基态时,将跃迁时释放的能量交给某一内层电子,使此内层电子电离而形成空位(被电离的电子称为内转换电子)。214Po的原子核从某一激发态回到基态时,可将能量E0=1.416MeV交给内层电子(如K、L、M层电子,K、L、M标记原子中最靠近核的三个电子层)使其电离。实验测得从214Po原子的K、L、M层电离出的电子的动能分别为Ek=1.323MeV、EL=1.399MeV、EM=1.412MeV。则可能发射的特征X射线的能量为 [ ]

A. 0.013MeV

B. 0.017MeV

C. 0.076MeV

D. 0.093MeV

答案

AC

完形填空
Earthquakes are common, and thousands of them happen each day.  But most are too weak to feel. During a  earthquake, there is often a great noise first.  Then the earth  terribly and many houses   down.  Railway tracks break and trains go off lines. A great many factories are destroyed. Thousands of deaths are caused, and many more lose homes.  Besides the great damage and deaths caused by the earthquake  ,other accidents such as fires often    . More buildings are destroyed and more deaths caused. It is well-known of the  of an earthquake, and for centuries man has been making researches on earthquakes. More than 2,000 years ago, ,a Chinese scientist named Zhang Heng invented a machine which could    from which direction the seismic waves(地动波)had come, and this machine is still   by scientists today. Now we know much more about earthquakes and   they happen, but we still can't tell exactly when and where earthquake will happen,  and cannot stop it from happening.
小题1:
A.realB.weakC.bigD.small
小题2:
A.movesB.shakesC.jumpsD.breaks
小题3:
A.getB.putC.setD.fall
小题4:
A.lonelyB.laterC.themselvesD.itself
小题5:
A.followB.copyC.comeD.enter
小题6:
A.information B.questions C.dangersD.troubles
小题7:
A.as a resultB.in factC.for exampleD.as well
小题8:
A.find outB.think up C.point atD.look for
小题9:
A.improved B.repairedC.protected D.used
小题10:
A.whereB.whyC.whatD.when
单项选择题