14. When did cyanobacteria start producing pure oxygen? O A. After the Hadean eon
O B. During the Hadean eon
O C. After the Proterozoic eon
O D. During the Phanerozoic eon

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Which of the layers of the earth has the following three characteristics? i. it is made of molten rock. ii. it has currents that are constantly moving. iii. earth’s plates float on top of its currents.

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