All carbon footprints are hard or impossible to pin down accurately, but the Internet is a particularly complex case.

所有的碳足迹都很难或者不太可能精确地算出来，对于互联网，情况更是复杂。

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See, the firing pin is the key to the whole case!

瞧，那撞针是整个枪的关键！

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If it is successful (in this case, the PIN returned by Twitter), it will get an access token with which the client can update the Twitter status on the user's behalf.

如果成功了(在这种情况下，Twitter返回了PIN)，就会获得一个访问令牌，客户端可使用此访问令牌代表用户更新Twitter状态。

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The interesting thing about Descartes' argument is that it's easy to see something has gone wrong in the case of the Morning Star and the Evening Star, but it's difficult to pin down what exactly went wrong.

笛卡尔论证的奇妙之处在于,我们能明显感觉到,晨星和昏星的例子中,有些东西不对劲,但很难确定,错误到底在出哪里

耶鲁公开课 - 死亡课程节选

Behind the scenes, the president's aides admit they were concerned the defense seemed to pin so much of its case on the president's testimony, but they say they were relived when the prosecution itself discredited Hale.

CNN: By Jill Dougherty/

"In this case, it will always be an open question until we can pin down what dark matter is made of, " he said.

CNN: Space station detector gives first clues to 'dark matter'

And sometimes, as is the case with the increasingly prevalent mobile supper clubs, you might not even be able to pin down their location.

BBC: Hong Kong��s secret nightlife spots