21．Mr. Morgan can be very sad ______, though in public he is extremely cheerful.
A．by himself  B．in person
C．in private  D．a(chǎn)s individual

22．By the time he arrives in Beijing, we ______ here for two days.
A．have been staying  B．have stayed
C．shall stay  D．will have stayed

23．This kind of glasses manufactured by experienced craftsmen ______ comfortably.
A．is worn  B．wears
C．wearing  D．a(chǎn)re worn

24．Floods cause billions of dollars worth of property damage ______.
A．relatively  B．a(chǎn)ctually
C．a(chǎn)nnually  D．comparatively

25．Americans eat ______ as they actually need every day.
A．twice as much protein  B．twice protein as much twice
C．twice protein as much  D．protein as twice much