1．Proper, scientific study of the impacts of dams and of the cost and benefits of controlling water can help to resolve these conflicts.
　　【译文】对于水坝的影响作用、水坝控制水流的成本和收益，应该进行恰当而科学的研究，这样才有助于解决这些矛盾。

　　【析句】 句子的主干是study... can help to resolve conflicts。主语的修饰成分较长，注意study包括两个方面的内容，一是the impacts of dams，一是the cost and benefits of controlling water。

　　【讲词】impact意为“碰撞，撞击；影响”，作名词时较多表示“影响”。
　　This books illustrates the impact of modern science upon society as a whole.（这本书阐述现代科学对整个社会的影响。）
　　The impact on the rate of inflation will be felt in 2005.（人们将在2005年感受到通货膨胀的影响。）

　　resolve作动词时意为“解决；决定；溶解；变成”，作名词时表示“决心”。
　　The circumstances resolved him to take the case to the Supreme Court.（在这种情况下，他决定把官司打到最高法院）。
　　The discussion resolved itself into an argument.（讨论到后来变成了争论。）
　　He made a resolve to launch a reform in the firm.（他决定在公司推进改革。）

　　2．While there are almost as many definitions of history as there are historians, modern practice most closely conforms to one that sees history as the attempt to recreate and explain the significant events of the past.
　　【译文】几乎每个历史学家对史学都有自己的界定，但现代史学家的实践最趋向于认为历史学是试图重现过去的重大史实并对其做出解释。

　　【析句】这是一个复合句，主句是modern practice most closely conforms to one that sees history as the attempt to recreate and explain the significant events of the past，从句是While there are almost as many definitions of history as there are historians。在While引导的状语从句中，又含有一个由as... as引导的从句，表示一种比较关系。

　　【讲词】 recreate意为“再创造；再现”。Is it possible to recreate the situation which surfaced three years ago?（是否有可能再现三年前的情形？）recreate还可以表示“（使）得到休养；（使）得到娱乐”。