This week, as part of a new series called Living In the Middle, NPR takes a closer look at what it really means to be middle class in the U. S.

这一周，作为一个叫《生活在中产》的新系列中的一部分，NPR深入研究美国的中产阶级到底是什么意思。

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NASA's newest class of astronauts signed up knowing there'd be no U. S. rockets to launch them into space, at least not in the immediate future.

NASA的最新宇航员被告知并不会有美国的火箭送他们进入太空，至少短期内是这样的。

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Bring to class a memo or business letter that you have received since coming to the U. s.

带一份你来美国后收到的一封商业信件或便笺到课堂上。

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U.S Army Sergeant First Class Brandon Lemmons says he passes along each day's information to his commanders, and they use it to map out their relief strategies.

VOA: standard.2010.01.30

You have half of your assets in one single asset class: U.S. Common stocks.

你将半数资产,投资于单一类别,美国普通股

耶鲁公开课 - 金融市场课程节选

Now, before, of course, in the first part of the class u we started out looking at u H and then looking at H not as functions of S and V or S and p, but as functions of temperature, mostly.

现在，在本课的前一部分,我们首先讨论了,然后讨论了,这两个量并未写成S和V或者S和p的函数，而是写成了温度的函数。

麻省理工公开课 - 热力学与动力学课程节选

Ross and his colleagues offered parallel columns of upper-class (U) speech versus the speech of (non-U) middle-class people trying to attain, or pretend to, upper-class status.

NEWYORKER: The English Wars

They've done a spectacular job for their clients and we continue--we're very excited about, one, we're excited about the region and two, we're excited to have a team of that quality doing real, on the ground research throughout China, which is, now, if you sort of look at the larger Chinese market, it's the second-largest market in the world, and there just aren't--there are many more world-class U.S. teams than there are world-class Chinese teams.

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We will foster greater cooperation with the private sector to provide a world-class U.S. travel experience.

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