完形填空

    Once there was a father and a son. They were ill-tempered(坏脾气的) and never gave way to  1 .One day the father 2 to ask some friends to dinner in his house. He 3 his son to buy some meat in town. When the son walked towards the town gate, a man was coming from the outside. The gate wasn't 4 enough to let two men in and out at the same time. But neither of 5 would give way to the other. They stood straight face to face inside the gate hour after hour. But the father was worried. “What shall I do? My son hasn't 6  yet. I can't wait any more.” He wanted to know what was the 7 with his son. So he left his friends at home, and went to town 8 his son. “You may first take the 9 home for my friends .Let me 10 here instead.” he said to his son when he knew what had happened.

潜水、登山和宇航都需要用到氧气是因为它能____ ；气焊、炼钢需要用到氧气是因为它能____ ．氮气的化学性质____ ，可用作____ ，氮气约占空气体积的　____ %．

__________ they are twins, they don't look the same at all.

仿写句子。
       如果你是一颗大树，就洒下一片绿荫；如果你是一株小草，就增添一份春色。                ，             ；               ，             。