問題詳情

29.Not until Kentucky's Mammoth Cave had been completely explored in 1972 _____.
(A) when was its full extent realized
(B) that its full extent realized
(C) was its full extent realized
(D) the realization of its full extent

參考答案

答案:C
難度:適中0.62963
統計:A(4),B(4),C(17),D(1),E(1)

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