[求助]OG-242

242. 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.

(A)  that no less than a technical or scientific breakthrough is necessary

(B)  that nothing other than a technical or scientific breakthrough is needed

(C)  that a technical or scientific breakthrough is necessary

(D)  the necessity for an occurrence of a technical or scientific breakthrough

(E)   the necessity for a technical or scientific breakthrough occurring

答案是C,解释说no less than 可以省掉,我不懂no less than在这里表达

什么意思,我觉得应该对technical or scientific breakthrough有限制

作用,为什么可以随随便便就去掉?