264. The invention of the coal-burning_______engine revolutionized industrial production in the 18th century and opened the way to the development of mechanized transport by rail and sea.
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.