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Earth's atmosphere is unique among the planets and is able to support life because it contains a large amount of ___________. A) oxygen B) helium C) methane D) carbon dioxide

User Sudheeshix
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Oxygen. Most living beings need air to breathe (and therefore live), and air (our atmosphere) contains about 21% oxygen.
User Jilles Van Gurp
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OXYGEN!!! What a great thing it is...
User Teamnorge
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