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What cawe learabout suenergy ithe 20th century and 21st century( )
· Solar output will reach its minimum ithe 21st century.
· Solar output ithe 20th century was the highest ihistory.
· Sunspot numbers iCycle 24 has reached its peak ithe 21st century.
· Sunspot numbers iCycle 24 is less thahalf those ithe 20th century.

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出自：运营管理

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