Runners who often manage to win races do so not only because they are good at running.

题目

Runners who often manage to win races do so not only because they are good at running.
这句话中 do so 是什么用法
我问的主要是so 的用法

答案

so在此是指代的作用,前面应该还有东西吧,用so省略了前面提过的“做...”