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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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 information coming out of Japan changes so frequently that it's difficult to pin down a specific level of radiation that residents are exposed to; in any case, levels vary from place to place.

日本传出的信息经常变化,以至于很难确定居民究竟暴露在怎样的辐射水平下;各种情形下不同的地方辐射水平变化不定。

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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

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"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