firstly,we should plant many trees to keep water.secondly,we can ride a bike or walk to the school and work.thridly,we shouldn't throw the dirty water into the river.fourthly,weshouldn't use the plastic bags.finally,we can ask more people to join us 这是五个句子,把它们整成两个,注意主要方法是从句和分词运用,不得删减内容,每句只有一个实质动词.还有两个半小时,拜托各位了