---I drove to Shanghai for the 2010 Expo last week. --- Is that_____ you had a few days off?
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.