molecule|molecules

这个氧分子由两个氧原子组成。

This oxygen ___molecule is made up of two oxygen atoms.

水分子由两个氢原子和一个氧原子组成。

Water ___molecules consist of two hydrogen atoms and one oxygen atom.

他的解释里连一丝诚意都没有。

There wasn't a ___molecule of sincerity in his explanation.