问题补充：
It was back home after the experiment.
A. not until midnight did he go
B. until midnight that he didn’t go
C. not until midnight that he went
D. until midnight when he didn’t go
答案：
A. not until midnight did he go
B. until midnight that he didn’t go
(答案→)C. not until midnight that he went
D. until midnight when he didn’t go
解析：考查强调句型。句意：直到半夜，他才做完实验回到家里。It is/was...that强调not...until句型时，not until要连在一起，排除B、D；A项缺少that，排除A，故选C。
