20. -Waiter!

-________?

-I can’t eat this. It’s too salty.

　　 A. Yes, sir　　　 B. What　　 　C. All right　　 D. Pardon

19.It was ______ back home after the experiment.

　　　 A. not until midnight did he go　　　　　　　　　 B. until midnight when he didn’t go

　　　 C. until midnight that he didn’t go　　　　　　　 D. not until midnight that he went