Mark the sentence that is closest in meaning to each of the following questions or indicate the correct answer to each of them . Not until Kentucky’s Mammoth Cave had been completely explore
Mark the sentence that is closest in meaning to each of the following questions or indicate the correct answer to each of them .
Not until Kentucky’s Mammoth Cave had been completely explored in 1972 …………………….
A. when was its full extent realized
B. the realization of its full extent
C. was its full extent realized
D. that its full extent was realized