Back up 可以表示支持某人或其说法，用事实佐证主张，或复制数据作备份。争论或会议中，back someone up 是站在对方一边；作文中，back up an argument 是用例子或数字支持论点；back up files 则是复制文件，以防出现问题。
想在对话中用 back up 吗？
写一句英语，查看错误和更自然的表达建议。
本次检查比平时稍久，完成后反馈会自动显示在这里。
back + person + up; back up + claim/argument + with + evidence; back up + files/data; a backup (noun)
- When the client blamed me for the delay, my manager backed me up.
- I back up my photos to an external drive every Sunday evening.
- The researchers backed up their claims with data from three different countries.
修改原因
修改前In your essay, back up each idea by a real example.
修改后In your essay, back up each idea with a real example.
说明用什么材料支持观点时，用 with：back up each idea with a real example。By 后可以接 -ing 动作：back it up by giving an example；被动句中也可以用 by 引出提供支持的材料：The claim is backed up by data。
Back down 看起来相近，意思却几乎相反：在争论中退让、放弃立场。比较：My colleagues backed me up, so I didn't back down。
动手练习
Before the system update, IT asked everyone to ___ their files.
查看答案
back up — To 后面需要动词，因此写成两个词：to back up their files。连写的 backup 是名词或形容词，例如 make a backup、a backup copy。
为远程办公的优点或缺点写一个论点，再用一个具体的亲身经历支持它。
Remote work can save a lot of time, and I can back this up with my own experience: I no longer spend ninety minutes a day on the bus.
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用正在学的词造句。LetsWords 检查用法和语法，提供修改与母语解释，再通过复习巩固。