根据短文内容，选择相应的词用它的正确形式补全短文。
decide against they run job profession hobby agree grow train |
Many teenagers have ____. But sometimes these can get in the way of ____ schoolwork. Liu Yu is a ____ star on his school team. His dream is to be a ____ runner when he ____ up. His parents won't allow him ____ so much although they have nothing ____ running. They think their son needs to think about other possible____. Liu Yu ____ with them. He thinks his parents are too strict with him. He also thinks it's very important ____ for himself. Only in this way can he have a chance to achieve his dream.
的实木材料制成木模，木模的质量为1.8kg．再用密度为
的合金铸造30个这样的工件，这些合金的总质量为648kg，则木模与合金材料密度之比为( )