Do you know how it is when you see someone yawn and you start yawning too?

当你看到有人打哈欠时，你也会开始打哈欠，你知道这是怎么回事吗?

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The brain is as active during REM (rapid eye movement) sleep when most vivid dreams occur as it is when fully awake, says Dr. Eric Nofzinger at the University of Pittsburgh.

匹兹堡大学的艾瑞克·诺夫辛格博士说，大脑在快速眼动睡眠期和完全清醒时一样活跃，大多数最生动的梦都发生在这个时候。

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It is when the villagers choose a queen.

是时候让村民们选出女王了。

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One belief is that it started when an English stableman committed suicide by hanging himself while standing on a pail,or bucket.

VOA: special.2011.06.05

This is one picture that probably you all know what it is when you see it, it's a familiar looking image.

这张图片,一眼便知其中乾坤,太眼熟了

耶鲁公开课 - 生物医学工程探索课程节选

That's not really what I think, but that's how disturbing it is when people talk, and very nice students who do not realize this often disrupt my line of thinking.

虽然那不是我的真实想法,但是在课上有人讲话确实很烦人,有些好学生也没有意识到这点,他们经常会打断我的思路

耶鲁公开课 - 基础物理课程节选

"It is when a mother trusts her judgement that she is at her best, " he said.

BBC: Six childcare gurus who have changed parenting

It is alright when it is warm, but gives your gums a good exercise when cold.

NPR: Discovering Afghan Cuisine, a World Away

First, to have the technology and not use it is when available is wasteful.

FORBES: Baseball's Unwillingness to Expand Instant Replay is Bad Business