Unit 4 Save the trees一、词汇1. fight v._ 过去时 _ 过去分词_They help fight against pollution.fight against 对抗,反对,与作斗争fight with 与打架 fight for 为而斗争/奋斗 用以上词的正确形式填空:(1)They were good friends, but sometimes they _ _ each other.(2)We should _ _ pollution so that we may have a clean world.(3)As a young student, he must _ hard _ his future.2. harmful adj. _They take in harmful ga