当这(氧气)开始在大气中积聚时，2.5亿年前，它让地球降温并且还杀死了一些形式的生命。
When this eventually began to accumulate in atmosphere, 2.5 billion years ago, it cooled the planet and killed some life forms.
当这(氧气)开始在大气中积聚时，2.5亿年前，它让地球降温并且还杀死了一些形式的生命。
When this eventually began to accumulate in atmosphere, 2.5 billion years ago, it cooled the planet and killed some life forms.
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