Old mice don't have car keys to lose track of, but they do struggle to remember a place where they once received a nasty shock or a hidden platform in a pool of murky water.

当然小鼠没有汽车钥匙可以遗失，但是通过训练他们能记得曾经的一个地方，那就是它们被轻微电击或忽然间木板敞开让它们落入水中的地方。

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Hidden in one of the glasses is a slice of lemon. Watch closely and track the glasses.

其中一个杯子里藏有一片柠檬，仔细观察并跟踪那个杯子。

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Defective shunting of track circuit constitutes a huge hidden trouble to the transportation production.

轨道电路分路不良对运输生产构成巨大的安全隐患。

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The Cure, meanwhile, wrote a short instrumental called The Weedy Burtons, which featured as a hidden track on their debut album Three Imaginary Boys in 1979.

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But on an auxiliary (and sometimes hidden) track employees can use a brokerage window to buy thousands of different mutual funds and usually exchange-traded funds and individual stocks, too.

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When the thrill of being unplugged outweighs the danger of losing essential data, there are a number of technologies that make it easier to back up those files, keep them hidden and even track down the missing computer itself.

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