-Listen! Is Mary playing the piano in the room?  --No. It ________ be Mary. She has gone to Hong Kong.

Though _______ money, his parents managed to send him abroad.

—Where did you meet him?—I met him on a number eleven bus, if you       know.

—Can I pay the bill by check?—Sorry，sir．But it's the management rules of our hotel that payment     be made in cash．

As it turned out to be a problem of no importance , we     so much time looking into it .