the most important thing is to keep safe and behave yourselfs on the way

问题描述:

the most important thing is to keep safe and behave yourselfs on the way
为什么thing不用复数

因为the most限定了只能有一个.
如果你说有很多things可以用
One of the most important things is to keep.
one of the most...代表最XX的事情之一