A:Na+ 1s22s22p63s2
B:F 1s22s22p5
C:O2﹣ 1s22s22p6
D:Ar 1s22s22p63s23p6
①小狗天天都炼习。____
②他已经学得想当不错。____
③子弹察过小狗的耳边。____
我国各民族的分布特点是( )