Also included will be any variations that have arisen from volcanic activity, solar activity, and, possibly, human activities.

这还将包括火山活动、太阳活动，可能还有人类活动引起的任何变化。

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They become completely involved in an activity for its own sake rather than for what may result from the activity, such as money or prestige.

他们完全是为了活动本身而参与活动，而不是为了活动可能带来的结果，如金钱或声望。

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You might need an activity that does nothing at all, such as when you have a construction that requires an activity, but there is no work to be done.

您可能需要一个根本不执行任何工作的活动，例如，当您拥有一个需要某个活动的构造，但没有要执行的任何工作时。

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