名词
中文翻译：坑洞
同义词：
['hole', 'pit', 'crevice', 'fissure']
例句：
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1. The rock formation is a natural pit prop.
这个岩石构造是一个天然的坑洞。
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2. The cavern was filled with water and had been used as a pit prop for centuries.
这个洞穴被水填满，并且几个世纪以来一直用作坑洞。
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3. The miners were digging deeper into the pit prop when they heard a loud noise.
矿工们正在挖掘更深的坑洞时，听到了一声巨响。