so much electrical equipment , wood and paper in one place , there is a danger of fire .
__ many times, but she still didn't know how to do it.
Scientists think that the continents ____ always where they ___today.
--- Would you tell me ___ you want your tea, with sugar or milk?--- Sugar, please.
Leaves are found on all kinds of trees, but they differ greatly __ size and shape.
He began to take political science_____ only when he left school.