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1·The absence of oxygen on other planets means that those planets lack an ozone shield to protect life forms against UV radiation.

其他行星上没有氧气，这意味着这些行星缺乏保护生命体免受紫外线辐射的臭氧层。

2·The absence of an oxygen atmosphere on Mars and other planets in our solar system means that these planets also lack an ozone shield that would protect surface-dwelling life from UV radiation.

在火星和我们太阳系的其他行星上没有氧气，这意味着这些行星也缺乏保护地表生物免受紫外线辐射的臭氧层。

3·They must campaign to repair the ozone shield, halt the greenhouse effect, preserve soil and save the tropical rainforest.

他们为了修护臭氧层，遏止温室效应，保护土壤和拯救热带雨林，必须奔走游说。

4·They must campaign to repair the ozone shield, halt the greenhouse effect, preserve soils and save the tropical rainforest.

他们为了修护臭氧层，遏止温室效应，保护土壤和拯救热带雨林，必须奔走游说。