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：考察强调句型。本文强调的是not until引导的时间状语从句。原句为：He didn’t go back home after the experiment until midnight.对其中的时间状语从句进行强调，故C正确。
