化学污染将威胁农业和食物链，进而危害人类健康。
Chemical pollution will bring about a threat to agriculture and food chain, and consequently to human health.
和动物一样，人类进化出了一套复杂的机制，来处理有关潜在威胁的信息。
Like animals, humans evolved with an elaborate mechanism for processing information about potential threats.
研究人员猜测，这些乌鸦从父母和鸦群的其它成员那里学会了辨认有威胁的人类。
The researchers hypothesize that crows learn to recognize threatening humans from both parents and others in their flock.
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