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

There is a comfortable chair to sit on .为什么加on the chair is comfortable to sit on为什么要加on? chair is comfortable to sit on 还是in ? the chair is very comfortable to sit in 这个地方为什么要用in而不用on The chair is comfortable to sit on/还是to be sat on? The chair is too dirty to sit on.为什么要加on呢? 英语语法问题为什么句子"She find a chair to sit on."中"sit"后还要加"on",可以直接说 there is no chair for me to （sit） 还是 （sit on） I found a chair to sit on A dog is on the chair A.sit B.sitting C.siting D.to sit the chair is soft to ____ 为什么要用SIT ON 不是BE SAT ON 帮个忙1.The couch is so comfortable to （）.A.sitB.be satC.sit on