名师点评
　　作者善于观察、善于思考，选取家乡小河的变化，说明环境污染带来的危害，并发出呼唤：要保护自然。
　　文章中很好地运用了已学到的语言材料、词语、句型等知识。如：one af ternoon，a friend of mine，used to do sth.，lots of, get there, throw...into...，after a while，out of，nothing but...，a lot of,，all over the world, no...or...等。文章中还用了状语从句、并列句、宾语从句、定语从句以及get.
　　现在谈谈标数码的几个句子：
　　①“Just before”应改用“when”才符合英语句法惯例。②“I thought to myself”应改成“I said to myself”才正确。因为在英语中“think to oneself”是“琢磨；沉思”之意，而“say to oneself是“想”，如：He said to himself that there was something wrong with the bike.他想自行车是出了毛病。③根据全文意思，这个句子应改成I knew：“The factories along the river often pour...which used to be in the river．”这样才符合时态一致性原则。

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