21. I hate ____ when people talk with their mouths full.
A. it B. that C. these D. them
22．Please tell me how the accident_____. I am still in the dark.
A. came by B. came out
C. came to D. came about
23．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
