21．The couple has their own reason for keeping their divorce _____ secret for ____ moment.
A．a; the B．the; the C．/; a D．a; a
22．What a pity! I ______ in Hongkong for three more days, but something urgent needed to be handled back home.
A．must have stayed B．could have stayed
C．may have stayed D．needn’t have stayed
