Because they know the secret to happiness.

因为他们知道快乐的秘密。

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They know how to choose happiness over depression, because they know how to deal with the problems of their lives.

他们知道如何选择快乐而不是沮丧，因为他们知道如何处理生活中的问题。

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"This is hard work, but people give freely of themselves because they know it's for them," said one mayor in Agadez.

“这项工作着实不易，但人们不计报酬地付出，因为他们知道这样做是为了他们自己。” 阿加德兹市的一位市长说。

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Older women might be less likely to delay because they know that the older they get, the higher the risks.

VOA: special.2010.08.11

The Athenians refuse to tolerate Socrates because they know he is not harmless, that he poses a challenge, a fundamental challenge to their way of life and all that they hold to be noble and worthwhile.

雅典人拒绝容忍苏格拉底,因为他们明白他并非无害，他公然挑衅，社会本质的生活方式,及他们视为崇高及值得的观念。

耶鲁公开课 - 政治哲学导论课程节选

because they know the types of students that go there.

因为他们知道去那里的学生类型。

选择 UCLA 的理由 - SpeakingMax英语口语达人

People observe a queue because they know what behaviour is expected of them to maintain order.

BBC: Who, what, why: How to get off a busy train

True entrepreneurs are OK with taking a risk because they know the rewards greatly outweigh them.

FORBES: What's Holding You Back?

Because they know the kind of sacrifices that you all make every single day.

WHITEHOUSE: Walter E. Washington Convention Center Washington, D.C.