What do you use and in what circumstances do you use it?

你使用什么样的搜索引擎，什么情况下会使用？

youdao

You were right to do what you did, under the circumstances.

在那种情况下，你所做的是对的。

《柯林斯英汉双解大词典》

No matter what the current circumstances are, there are plenty of things you can do from your side by working on yourself, increasing your value, and preparing yourself for the right opportunity.

不管目前的情况怎样，总有些事情你可以从身边做起，去完善自己、提升价值，并为合适的机会做准备。

youdao

In what circumstances do you notify a Twitter user that you have handed over his or her information?

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That basic idea that if you work hard, no matter where you come from, no matter what you look like, no matter what the circumstances of your birth, if you work hard you can do well enough to raise a family and own a home, send your own kids to college, put a little bit away for retirement.

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Focus on what you can do within your circumstances, rather than wait for ideal conditions.

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