考博考试

试题来源：南京大学真题2006年
【单选题】 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 realimtion of its full extent

参考答案：C
网考网解析：
not until结构位于句首时，主句部分需要倒装，选项C正确。 ... 查看试题解析出处>>