Perhaps at one time, the baring of teeth sometimes apparent in yawning could have been an aggressive act.

或许从前，打哈欠有时明显地露出牙齿可能就是一种挑衅行为。

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In a 1988 study, University of Zurich ethnologist Edward Stammbach set up an experiment with long-tailed macaque monkeys to test their ability to rein in aggressive behavior and act cooperatively.

在一项1988年的研究中，苏黎世大学的人种学者爱德华·斯塔姆贝奇对长尾猕猴进行了一次试验，以测试它们控制攻击性的行为和相互合作的能力。

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Scott Wiener, a supervisor and an advocate for more aggressive law enforcement, said his constituents were urging him to act.

斯科特·威纳(Scott Wiener)是一名监督员，他主张加强执法，称选民们敦促他采取行动。

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One local councillor condemned the move as an aggressive act against Sydney's lesbian and gay community.

BBC: Sydney row over removal of rainbow road crossing

In 2001, Mr. Spitzer used the Martin Act, an aggressive New York state law created in 1921, to shed light on Wall Street's research practices.

WSJ: When Regulators Go Rogue

They revealed an unwillingness to share data which broke the spirit, if not the letter, of Britain's Freedom of Information act, an aggressive attitude to the peer review of papers by opponents and an apparent willingness to hedge science in the face of politics.

ECONOMIST: Climate science