Because early Earth lacked oxygen in its atmosphere, it also lacked a protective ozone barrier.

因为早期的地球大气中缺乏氧气，所以也缺乏起保护作用的臭氧层屏障。

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Because early Earth lacked oxygen in its atmosphere, it also lacked a protective ozone barrier.

因为早期的地球大气中缺乏氧气，所以也缺乏起保护作用的臭氧层屏障。

youdao