So the need to quickly recognise things that could be helpful or harmful could have had a great influence on rock art and explain why some images are more common across cultures than others.

因此，快速识别事物是有益还是有害的需求可能对摇滚艺术产生了巨大的影响，并解释了为什么一些形象在不同文化中比其他的更常见。

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She can either be helpful or harmful to mankind.

她对人类可以是有益的，也可以是有害的。

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Pegging another person as helpful or harmful is crucial when choosing friends. And that ability starts early.

择友的时候，判别某个人会给自己带来帮助还是伤害很重要；人们在很小的时候就具备这种本领了。

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And like all tools, it can be helpful or harmful depending on how we use them.

CNN: Computers can't replace real teachers