阿摩線上測驗
19. Not until Kentucky’s Mammoth Cave had been^completely explored in 1972 _____.
(A) when was its full extent realized
(B)was its full extent realized
(C) that its full extent was realized
(D)the realization of its full extent
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統計： A(13), B(96), C(27), D(3), E(0) #923647
統計： A(13), B(96), C(27), D(3), E(0) #923647
