在GMAT语法考试中经常会出现由于连接词的改变而导致句意改变的题目，如果对于连接词掌握不好的话，很容易出现误判，今天小编就给大家介绍下GMAT语法连接词中while与but的区别，快来了解一下吧！
while引导的从句：
意思是“当…时”，放句首或句中
意思是“转折对比contrast”时，多放在句中，也可以放在句首。
while表示对比概念的时候，两个事物要是同时发生。
意思是“虽然、尽管”(让步)时，多放在句首。(=although)
表示条件,意为"只要",其意思和用法相当于as long as。while可位于句首,也可位于句中。
真题解析
真题1：
After several years of rapid growth,the healthy care company became one of the largest health care providers in the metropolitan area,while it then proved unable to handle the increase in business,falling months behind in its payment to doctors and hospitals.
A.while it then proved unable to handle the increase in business,falling months behind in its payment to
B.while it then proved unable to handle the increase in business and fell months behind in its payment to
C.but then it proved unable to handle the increase in business,falling months behind in its paying
D.but then proving unable to handle the increase in business,falling months behind in paying
E.but then proved unable to handle the increase in business,falling months behind in paying
翻译：
几年的飞速发展之后，健康护理公司成为这个大城市最大的健康公司之一，然而之后却不能很好地处理快速成长的事业，好几个月没有付医生和整个医院工资
句式：
the company became one of the largest providers,but then proved unable to handle sth.,falling months behind in panying
思路：
考察转折
选项：
A.即便表示转折对比，while也有"at the same time"的含义在里面，与then矛盾，并让句意变成了the health care company expanding and falling是同时发生的，但是实际上应该是先became largest，然后再fell;
B.同B，并且fell和proved形成并列，逻辑不对;
C.前面的it多余，可以省略(effctiveness);in its paying，使得paying从动词变成了动名词，不简洁，prep.+one's+doing往往是不简洁的。paying这个动作就是the health care company执行的，所以不用加上its;
D.but要连接两个句子或谓语，proving改变了逻辑;
E.正确。
真题2:
Building large new hospitals in the bistate area would constitute a wasteful use of resources,on the basis of avoidance of duplicated facilities alone.
A.on the basis of avoidance of duplicated facilities alone
B.on the grounds of avoiding duplicated facilities alone
C.solely in that duplicated facilities should be avoided
D.while the duplication of facilities should be avoided
E.if only because the duplication of facilities should be avoided
翻译：
如果仅仅因为是这些设施的重复应该被避免，那么在B这个区域建又大又新的医院将会是一种资源的浪费。
句式：
Building X would constitute a wasteful use of Y,(modifier).
思路：
通过意思来理解句子意思;前面说了一件事，后面解释了一个原因。
选项：
A.'on the basis of x'这个短语中会默认为X已经存在了,但是A没有出现问题，所以选择错误;介词两个一般会造成修饰错误;
B.avoiding duplicated facilities语义逻辑错误，文章强调的是避免重复而并非避免工厂;强调重心发生变化;avoid的逻辑主语错误;
C.avoiding duplicated facilities语义逻辑错误，文章强调的是避免重复而并非避免工厂;强调重心发生变化;avoid的逻辑主语错误
D.同样改变句子意思，原本是通过一个修饰成分说明为什么building是不好的;但是WHILE却出现了转折的意思;
E.正确。
真题3：
Industrialization and modern methods of insect control have improved the standard of living around the globe while at the same time they have introduced some 100,000 dangerous chemical pollutants,having gone virtually unregulated since they were developed more than 50 years ago.
A.while at the same time they have introduced some 100,000 dangerous chemical pollutants,having
B.while at the same time introducing some 100,000 dangerous chemical pollutants that have
C.while they have introduced some 100,000 dangerous chemical pollutants at the same time,which have
D.but introducing some 100,000 dangerous chemical pollutants at the same time that have
E.but at the same time introducing some 100,000 dangerous chemical pollutant,having
翻译：
工业化的杀虫方法提高了人们的生活水平而于此同时这些方法也引入了一些化学污染物，这些化学污染物没有得到有效的管理。
句式：
Industrialization and modern methods…have improved…while introducing…
思路：
While和but的区别，一个可以加动名词，一个不可以;还有代词指代的问题。
选项：
A.Having修饰主语IM methods，逻辑语义错误，应该修饰污染物;整个句子中的两个代词they指代对象不一致，划线部分they没有指代对象，未划线部分的they指代的是pollutants;
B.正确;
C."introduced 100,000 dangerous chemical pollutants at the same time"表示的是这么多化学物质被同时引入;但是逻辑语义只是强调了污染物被引入是一个什么样的影响;整个句子中的两个代词they指代对象不一致，划线部分they没有指代对象，未划线部分的they指代的是pollutants;
D.Introducing和have improved不平行;but需要前后平行，while不需要;
E.having gone…分词结构有作伴随状语修饰have introduced的歧义，而不是作pollutants的定语。