教學過程中經常遇到學生對于長難句的分析和理解不到位的情況，長難句的分析和理解會影響學生在托福閱讀的理解，尤其是在句子簡化題。這次題目解析針對于TPO的一個長難句：

　　Sediments are also dropped where a river slows on entering a lake or the sea, the deposited sediments are on a lake floor or the seafloor at first, but will be located inland at some future date, when the sea level falls or the land rises; such beds are sometimes thousands of meters thick.

　　難句類型： 復雜修飾+插入成分

　　本句的主句結構應當是Sediments are also dropped，but will be located inland at some future date; such beds are sometimes thousands of meters thick. 這是一個由分號隔開的并列句，分號前面的句子結構比較復雜，Sediments are also dropped ，后面跟了一個由where引導的狀語從句，緊接著這個狀語從句又加上了一個插入結構， the deposited sediments are on a lake floor or the seafloor at first， 然后才開始進行轉折but will be located inland at some future date， 但是馬上又跟上了一個由when 引導的狀語從句。分號后面的半句比較簡單 such beds are sometimes thousands of meters thick.同學們面對這樣的句子一定要先找主干，把狀語從句、插入結構紛紛跳過，從紛繁復雜的句子中找出主干來，才能不被ETS出題人改寫的句子所迷惑。

　　譯文：

　　當河流匯入湖泊和海洋的時候也會有沉淀，這些沉淀最初在湖底或海底，但將來海平面下降或者陸地崛起時，它們就會分布于內陸，通常厚達幾千米。

　　意群訓練：

　　Sediments are also dropped where a river slows on entering a lake or the sea, the deposited sediments are on a lake floor or the seafloor at first, but will be located inland at some future date, when the sea level falls or the land rises; such beds are sometimes thousands of meters thick.