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While electricity exists as separate charges, like the plus and minus of a battery, magnets always come in a joined pair;

电可以作为分开的电荷存在，比如说电池的正极与负极，而磁则总是要成双成对地出现。

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A crunch could come in the next few months, as foreigners gather for a pair of summits on Afghanistan, first in Istanbul in November, then in Bonn in December.

接下来几个月可能出现危机，因为许多外国人会就阿富汗问题参加两个峰会，第一个是于11月在伊斯坦布尔召开，随后是于12月在波恩。

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If I do come in 2012, I will invest in a pair of decent black snow boots, elegant enough to wear with suits and skirts, at least during the day.

FORBES: Exclusion and Inclusion at Davos

They also come in three pairs, one member of each pair being measurably heavy (though lighter than a quark) and one being of minuscule mass.

ECONOMIST: Particle physics makes sense, but it assumes too much

Come Sunday the pair have will have met in four straight Slam finals, with Djokovic already winning at Wimbledon, the U.S. Open and in Australia, where the 25-year-old Serbian outlasted Nadal in a nearly six-hour epic.

WSJ: Belmont Loses, Tennis Has Another