A third type of mountain may be formed as a result of volcanic activity which occurs in regions of active fold mountain belts, such as in the Cascade Range of western North America.

第三种类型的山可能是由于火山活动形成的，一般发生在活动性褶皱带地区，如北美西部的喀斯喀特山脉。

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Only if you take an active part in physical activity will you be able to keep fit and stay healthy.

你只有积极参加体育锻炼，才能保持身体健康。

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School students should have at least three hours of active physical activity each week.

学生每周至少应该有三个小时的体育活动。

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"Because there are only a couple of previous records of eruption at this particular volcano, it is difficult to judge either how long the activity will go on there, or how long the volcano might then be dormant before it goes active again."

VOA: standard.2010.04.15

It's as if "thinking nothing" is not a passive activity, but an active one.

好像“脑子里一片空白“,不是一种被动行为，而是主动的似的。

耶鲁公开课 - 1945年后的美国小说课程节选

The company says it tracks three primary metrics of user activity: daily active users, monthly active users, and monthly active users.

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Retail activity was the most active all week as investors get comfortable with lower yields.

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It needs to develop its own programs to monitor market activity and become an active part in preventing the next global meltdown.

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