Covering 71 percent of Earth's surface, the oceans play an essential role in maintaining the conditions for human existence on land, moderating temperature by the absorption of heat and carbon dioxide, and giving pure water back to the atmosphere through evaporation.
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ACovering 71 percent of Earth's surface, the oceans play an essential role in maintaining the conditions for human existence on land, moderating
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BCovering 71 percent of Earth's surface and playing an essential role in maintaining the conditions for human existence on land, the oceans moderate
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CThe oceans cover 71 percent of Earth's surface and play an essential role in maintaining conditions for human existence on land, and by moderating
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DThe oceans cover 71 percent of Earth's surface, play an essential role in maintaining the conditions for human existence on land, and moderate
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EThe oceans cover 71 percent of Earth's surface, playing an essential role in maintaining the conditions for human existence on land, and they moderate
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正确答案: A