16.I prefer a _______ typewriter to an automatic one.
A. mechanic B.manual C.merchant D.mental
17.If you want to stop for a moment, just press the ‘_______’ button on your tape recorder.
A. toilet B.thumb C.violin D.pause
20.I have _______ three terrible English examinations this week.
A. observed B.operated C.undergone D.suffered
16.B 17.D 18.D 19.A 20.C