21．The boss wanted an assistant with
A．a；不填 B．the；he C．a；the D．the；不填
22．It is a set rule that all payments ______ be made by the end of the month.
A．will B．shall C．can D．may
23．—Will you join us in the game?
—Thank you, _________ I’m busy preparing for my examinations.
but why not? B. but I’d rather not.
C. and I won’t. D. and I’ll join.