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Home Q & A Board Science-Related Homework Help Geography and Earth Sciences
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riveraes riveraes
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6 years ago

At the beginning of the Proterozoic, Earths atmosphere was mostly ____.
  a. oxygen
  b. nitrogen
  c. carbon dioxide
  d. water vapor
  e. argon
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tkelems2012tkelems2012
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6 years ago
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riveraes Author
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6 years ago
You make an excellent tutor!
alpheratz
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Yesterday
Good timing, thanks!
bahajo
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2 hours ago
Helped a lot
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