根据短文内容，用方框中所给单词的适当形式填空，每词限用一次。
Scientists would like to put a huge mirror in space above the earth. It might be sixty miles wide. It would be 小题1:to catch the rays of the sun. it would direct the sun’s rays on the earth as a child might do to make sunlight 小题2: on the wall with a hand mirror.
Why do they want to do this? The sun’s rays could be 小题3: in many ways. They could light up 小题4: by night. The warm rays could stop frosts(霜冻) which might come at night and hurt fruit and crops. They could melt（融化) 小题5: icebergs in the ocean. Perhaps they could change cloud movements and bring rain where it is needed.
小题1:used
小题2:dance
小题3:helpful
小题4:cities
小题5:dangerous
题目分析：
小题1:句意：它被用于捕捉太阳的射线。 be used to do sth. 被用于做某事。
小题2:句意：就像孩子用小镜子使阳光在墙上跳舞。 make +宾语+do sth. 使……做……。故此处用动词原形dance。
小题3:句意：太阳的光线在许多方面多很有用。根据They could light up可知此处是说阳光的和用途，又因位于be 动词后用形容词helpful。
小题4:句意：他们能在黑夜照亮城市。结合句意可知此处用名词复数cities 。
小题5:句意：他们能融化海洋里危险的冰川。修饰icebergs in the ocean.可知大洋里的冰山容易让船只翻船，因此是危险的，因修饰名词icebergs故用形容词dangerous。