25℃时,水的电离达到平衡:H2OH++OH-;△H>0,下列叙述正确的是( )
一群氢原子处于同一较高的激发态,它们向较低激发态或基态跃迁的过程中( )
All the parents ____ ____ their children's ____.
解方程组:x-y=42x+y=5