It was not until mid-night he went back home after the experiment.A. whenB. / C. thatD. b

问题补充：

It was not until mid-night he went back home after the experiment.

A. when

B. /

C. that

D. before

答案：

A. when

B. /

(答案→)C. that

D. before

解析：考查强调句型。这是对not until引导的时间状语进行强调，句型为：It was not until…that…。