21．My neighbor asked me to go for ______ walk， but I don’t think I’ve got ______ energy.
A．a; 不填 B．the; the C．不填；the D．a; the
22．Collecting stamps as a hobby___________ increasingly popular during the past fifty years.
A．becomes B．became C．has become D．had become
23．To everybody's surprise, the fashionable young lady ___________ to be a thief.
A．found out B．proved out C, put out D．turned out
