Call on 可以表示正式请求某人做某事，也可以表示短暂拜访。第一种意思中，人后面接 to + 动词：call on the government to act。这个结构常见于新闻、报告和作文，正式讲话中也用 call upon。表示拜访时，它略显正式，日常更常说 drop by 或 visit。
想在对话中用 call on 吗？
写一句英语，查看错误和更自然的表达建议。
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call on/upon + person + to + verb; call on + person (= visit briefly)
- The union has called on the company to review its pay policy this year.
- While we were in Leeds, we called on my aunt for a quick cup of tea.
- The head teacher called on parents to keep their cars away from the school gate.
修改原因
修改前The mayor called residents to save water during the hot summer.
修改后The mayor called on residents to save water during the hot summer.
没有 on，call 后面直接接居民，会被理解为给居民打电话或叫他们过来。这里要表达呼吁行动，结构是 call on + 人 + to + 动词。
Call on 后面接人；call for 后面接所要求的事物：The report calls for stricter rules。对比 The report calls on the government to introduce stricter rules。美国学校里，call on 也表示点名让学生回答：The teacher called on me first。
动手练习
In an open letter, scientists ___ world leaders to cut emissions faster.
查看答案
called on — 公开信呼吁领导人采取行动，所以选 called on。Called world leaders 会更像科学家给领导人打电话或召集他们，不能表达这里通过公开信发出呼吁。
写一个所在城市或社区的问题。说明你会呼吁谁解决，以及具体需要做什么。
Traffic near our school is dangerous, so I would call on the city council to build safe bike lanes.
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