Even their most ardent champions concede that no less than a technical or scientific breakthrough is necessary before solar cells can meet the goal of providing one percent of the nation's energy needs.
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Athat no less than a technical or scientific breakthrough is necessary
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Bthat nothing other than a technical or scientific breakthrough is needed
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Cthat a technical or scientific breakthrough is necessary
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Dthe necessity for an occurrence of a technical or scientific breakthrough
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Ethe necessity for a technical or scientific breakthrough occurring
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正确答案: C