H2O means that each water molecule contains one oxygen and two hydrogen atoms. H2O表示每个水分子含有一个氧原子和两个氢原子。
The map shows where you can get some H2O when you're out running. 这张地图显示你出去跑步时在哪里可以得到水。
The more scientists examine H2O, the stranger it starts to seem. 科学家们对水研究得越多,它就显得越奇怪。