(1) call for
① 来找(某人);来取(某物) I'll call for you at your house.
②要求;需要Success in school calls for much hard work.
(2) call on
① call on / upon sb. 拜访;去会(某人) I hope to call on you at your office at 3 o’clock today.
② call on / upon sb. to do sth. 请/叫某人做某事He called upon me to speak immediately.
③ 号召;呼吁;要求 The President called on his people to serve the country.
(3) call up
① 给……打电话 (英 ring up) I tried to call you up last night, but no one answered the phone.
② 征召入役;调用 (后备部队) Three boys in our street were called up last week.