21. How shall we celebrate _____ success of our experiment ?
We should enjoy ______ delicious lunch together.
A. 不填 ；不填 B. 不填； a C. the ; 不填 D. the ; a
22. He gave a clear ______ of his idea using a simple language, which made it easy for us to understand.
A. explanation B. impression C. conclusion D. instruction
