名词
中文翻译：警戒线
同义词：
['protective zone', 'security zone']
例句：
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1.The police cordoned off the area to guard against any further attacks.
警方封锁了该地区，以防进一步的攻击。
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2. The military has set up a guard plot around the base to prevent intruders.
军队在基地周围设立了警戒区，以防止入侵者。
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3.The border guards were posted at the entrance of the city to guard the perimeter.
边境守卫被部署在城市的入口处，以保护边界。