请问on call

请问on call 请问call on和call at有什么区别? 请问call at ,callfor.,call on,call up有什么区别? call on call on On Call call on , call for, call in ,call up 分别是什么意思? 请问call in 和call on都可以表示拜访某人,有何不同?Our salesmen call on their best account twice a month. We could call in on Patrick on the way to your mother's. call on 什么意思 用call on造句 用call on 造句 请问call for与call on的区别?两者都有要求的意思,有什么区别吗? 请问call in,call at,call on都有来访的意思,这三个词有什么区别吗?有例子说明一下更好了. 用call on 与 call at 如何区分call up 和call on call on与call at 的区别 call at a call on sb. call on,call in,call off的区别