It was not until mid-night they reached the camp site.A. thatB. whenC. whileD. before

问题补充：

It was not until mid-night they reached the camp site.

A. that

B. when

C. while

D. before

答案：

(答案→)A. that

B. when

C. while

D. before

解析：考查强调句型。本题强调的是时间状语not until mid-night；句意：直到半夜，他们才到达宿营地。故A正确。要注意如果不使用强调句型，Not until mid-night did they reach the camp site。要使用部分倒装句。