The spy never told his family about his underground activities.

这位特务从未把他的机密运动通知家里人。

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The most common approach to extracting metal-bearing ore from a porphyry copper deposit is by open-pit mining, although such mines also typically include some underground activities.

从斑岩含铜矿床开采含金属的矿石，最主要的方式是露天开采，尽管这种矿床常会伴随一些地下的地质活动。

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"If all such activities go underground, they would be more difficult to control," Lee says, potentially opening a greater market for trafficking.

Lee指出，如果所有活动都转入地下的话，监管会更加困难，而且还可能会滋生一个更大的人口贩卖市场。

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The Obama campaign has repeatedly said that the Illinois Democrat repudiates the Weather Underground's activities.

CNN: Palin: Obama put 'ambition above country'

The main purpose of the seminar was to give an general idea of current state of ground water in Uzbekistan, scientific-educational activities and the area of usage of underground water and determination of future trends relating to improvement of research methods and educational approaches with development of practical recommendations.

UNESCO: OFFICE IN TASHKENT