—Who______ it be that is knocking at the door? —It ______ be Father, but I’m not sure.
This is the best way ______ I have thought of ______ the problem.
Great attention must be paid ______ welfare, especially in the poor area.
At this time tomorrow ______ over the Atlantic.
Chen Xiexia is the first Chinese athlete ______ the gold medal in the Beijing Olympic Games.
______ many times, he finally understood it.