come across 与come upon的区别

come across 与come upon的区别 come across 与 come upon 的区别 都是偶然遇到的意思 come back,come by,come around与come across的区别 come from,come across,come to区别 by chance 与come across区别 come over,come up,come across,come to,come into的区别 come across的意思 come to 与come into 的区别 come out与come up的区别 come out与come about的区别 come on 与 come in 的区别 come along 与come about的区别?