I am on 为什么用on?

I am on 为什么用on? I am on a soccer team.为什么用on I am on cloud nine.为什么? I am keen on I am on the I am on i am on fto i am working on 英语on的问题I am leaving for Shanghai on business.这里面为什么用on连接 i am on it的意思请问I AM ON I am stuck on you! I am relying on you! i am down on my I am always on line I am tested on English. I am on the swim I am really gone on i am up on him