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

收报单位：“郑州、昆明铁路局部驻以上单位机车验收室、车辆验收室”，昆明局电报所投递（）封。

A、1

B、2

C、3

D、4