Aggression is a kind of innate survival mechanism, an instinct for self preservation, that allows animals to defend themselves from threats to their existence.

攻击性是一种天生的生存机制，一种自我保护的本能，使动物能够保护自己不受生存威胁。

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The researchers explained that the study demonstrated when we are in a novel environment the brain partly remains alert so that humans can defend themselves against any potential danger.

研究人员解释说，这项研究表明当我们处于新环境，大脑会保持部分警觉，这样人类就能在各种潜在的危险中保护自己。

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All our officers are trained to defend themselves against knife attacks.

我们所有的警察都接受过自卫训练，能够对付持刀袭击。

《牛津词典》

"The African Union charter says first that the people have the right to defend themselves against the oppression of a dictator,".

VOA: standard.2009.03.20

Everybody who could ran up to the acropolis to defend themselves.

届时每个人都可以去卫城来进行防御

耶鲁公开课 - 古希腊历史简介课程节选

In the case of Nimes, N-I-M-E-S, which was largely a Protestant town, they knocked down the wall so the Protestants of Nimes could not defend themselves against this all-conquering Catholic monarch.

以尼姆为例,那儿曾经是一座新教徒的城市,但统治者们拆毁了围墙,所以新教徒们再也无法对抗,所向无敌的天主教统治者了

耶鲁公开课 - 欧洲文明课程节选

They only felt safe in so far as they could defend themselves with their makeshift weapons.

CNN: MEDAN'S MADNESS

It focuses on a small colony of people struggling to defend themselves against the virals.

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Modern victims of bullying have a much broader arsenal of tools with which to defend themselves.

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