There is a comfortable chair to sit on .为什么加on

题目

There is a comfortable chair to sit on .为什么加on
而有的句子不加介词,像用take part而不用take part in
最好举几个例子,

答案

sit on the chair正如楼上说的是逻辑上的动宾关系而你问的我找了例句How many of you are going to take part?你们多少人准备参加?To take part in a wrestling match with.与（某人）一起参加摔跤比赛我们可以看出...