21．Mr．White, who comes from ____ European country, has formed _____habit of attending ____ church on Sundays．
A．an; /; the B．a; a; a C．an; the; / D．a; the; /
22．I would appreciate ______, to be frank, if the goods could be delivered as soon as possible．
A．you B．that C．it D．myself
23．By the time he retires, professor Baker _____ for almost forty years．
A．will have taught B．had taught
C．has taught D．is teaching
