文档介绍：
英语语法-代词的运用
代词在阅读过程中是难点之一。在英语中，为了语言的精练，幸免重复，除了采纳“省略”手段外，还广泛地用代词来代替上下文中已经出现过的词或提到的内容。在阅读过程中必需依据上下家难以进展试验的因素，而在同样的状况下，他的自然科学的同事们却可以进展试验。(it为形式宾语代替真正宾语to conduct．．．。)
3．The metallurgist has recently found a metal skin for missiles and supersonic planes，one that will retain its strength at the high temperature caused by air friction．
冶金学家最近独创了一种用于导弹和超音速飞机的金属外壳，这种外壳在大气摩擦引起的高温下仍旧能保持其强度。(one作同位语，代替skin。)
4．If one can scale down all dimensions to，let us say，one tenth，the average lengths of the current-paths will be reduced to one tenth．And the speed of operation will be scaled up 10 times．
假如人们能把全部尺寸缩小，比方说，减小到原来的1／10，那么电流路径的平均长度也将减小到1／10，操作速度因而就会按比例提高10倍。(one泛指人。)
5．Underground water reserves are much larger than those on the surface，but as they are unseen we tend to understimate them．
地下水的储量要比地面水大得多，但是由于看不到，所以往往低估了地下水的储量。(those代替reserves。as引导缘由状语从句。them代替reserves。)
6．Here we find that the term work has been given by science a somewhat more limited meaning than that to which we have been accustomed．
这里我们发觉，科学给予“功”这个词的含义比我们所习惯的“工作”这个词的含义多少要狭窄一些。(第一个that是连词，引导宾语从句。其次个that是代词，代替work。)
7．We know that air can be compressed， and it is reasonable to suppose that the air at the surface of the earth is co