All three of these words can be used to talk about actions or situations that take place at the same time. There are some differences.
Background action or situation
We can use all three words to introduce a longer background action or situation, which is/was going on when something else happens/happened. Note that we usually use a progressive tense for the longer background action or situation.
As-clauses usually introduce less important information. They most often go at the beginning.
As I was driving to work, I saw him walking down the street.
When- and while-clauses can go at the beginning or end of sentences.
I was having a bath when the telephone rang.
While they were having a nap, somebody broke into the house.
Simultaneous long events
While is used to say that two longer actions or situations go/went on at the same time. We can use progressive or simple tenses.
While he was watching TV, I was working.
He slept while I cooked supper.
As is used to refer to two situations which develop or change together. We normally use simple tenses.
As I get older, I get more optimistic.
As he came into the room, all rose to their feet.
When is used to refer to ages and periods of life.
His parents died when he was ten.
Simultaneous short events
To talk about two short actions or situations that happen/happened at the same time, we usually use as. When is also possible.
As I opened my eyes, I saw a strange sight.
Reduced clauses
It is often possible to drop subject + be after when and while.
Start when ready. (= Start when you are ready.)
问题：
The exchange between the teacher and the student promotes learning far different from that which results as the student listens but does not participate.
这个关于as的问题在以上材料中属于background action or situation的分类。
“the student listens but does not participate”不属于“不重要的”背景，所以根据语感换成when.
六、很重要的思想：句子和动词、名词、形容词和副词的跨级统一
（仅对sat写作够用）意思就是：①that+句子=名词、形容词
                              If/although…+句子=副词
                              动词+ing/ed=名词、形容词
                              ②名词→主语（S, subject, actor）、宾语(O, object)
                              形容词→定语
                              副词→宾语补足语


7. Because the garden was untended, the windows had no shutters, and the lawn overrun by weeds, people passing by the old house assumed that it was unoccupied.
第三个改成the lawn was overrun by weeds
Before
8. Q took D to De’s home for a visit, never imagining that five years would pass before seeing De again.
Would pass所以后面是he would see
插入语与其对应结构
9. An increasing number of students are coming to realize that an education at a public university can be as good, if no better, than an elite private college.
“, if no better,” 属插入语，对应前面的”be as good.” 这时候两个对应成分都要完整：be as good as和of no better than，才能使插入语起到完整的限定效果。所以是：can as good as, if no better than, one at an elite private college.
注意，平行的核心在于将有平行关系的事物独立出来：
打个比方：A, B, and C
               ↓对abc进行修饰
           Axyz, Bxyz, and Cxyz / xyzA, xyzB, and xyzC
10. The psychologist states that most people want the same things: interesting and meaningful work, respect, and their own love.
这三个事物本应是：work, respect, and love
分别的修饰是 interesting and meaningful, x, their own
因此这里明显不平行，their own是possessive pronoun不是adjective，要改成love of their own。
Like后面的东西
11. For most young people in America who are approaching voting age, choosing a president is very much like the process by which you choose a homecoming queen.
A is (like) B也可成为一种平行结构。[A=choosing a   president]→[B=choosing a homecoming queen].改完就是：choosing a homecoming queen.
(出现三次)12. Unlike 100 years ago, schoolteachers nowadays usually aspire to earn a good living.
必须要改成：Unlike their counterparts 100 years ago. 相当于counterparts与 schoolteachers平行。
13. Norwegian writer Sigrid Undest is like the novelist Sir Walter Scott in her use of historical backgrounds, but unlike his books, she dwells on the psychological aspects of her characters.
这句话的问题并不是指代不明。只有一男一女的话不会指代不明。
14. Like his other cookbooks, in his new book Chef Louis offers lenthy explanation of what he considers to be basic cooking principles.
调整语序后，[Chef Louis offers lenthy explanations (of…) in his new book]→[what he does in his other books]这样才平行：Chef Louis offers lenthy explanations与what he does平行，in his new book与in his other books平行。
But前后
15. The poet CM was a mative of Jamaica who spent most of his life in the United States but writing some of his poems in the Jamaica dialect.
此句并不符合平行原则，因为两个动词：spent, writing不平行。不做大改的话writing改成write就行。
词性平行
16. At graduation, the speakers assured us that our many courses in the liberal arts had prepared us equally well for the challenge of working and further study.
值得注意的是，虽然working和further study都是名词，但因前者是动名词，两者并不平行。Work和further study才算是平行。最好搞成of the challenge of work and of further study.
比较级前后对称问题(more than前后)
大部分情况与and/or一样，不能省略任何成分。有一例外：
17. With the LP, the US acquired a larger territory in area than if you combined Britain, France, Italy, Germany, Spain and Portugal.
应该是：Territory (which is) larger in area than (the territories of) B, F, I, G, S and P combined. 应该是省略了”territory.”
18. No one is sorrier but me that you missed the awards ceremony.
摘自：http://talk.collegeconfidential.com/sat-act-tests-test-preparation/87000-blue-book-writing-questions-writing-genuises.html


（正确答案sorrier than I）“Because “than I” implies “than I am.”” “We don't say "No one is sorrier than me am that you. . ."”
三、逻辑关系决定逻辑词
条件
Intimacy, love, and marrige are three different, if interrelated, subjects.
此句中if表示条件，而句子意思上也表明interrelated是条件。所以说这句子根本没错。
使必要(have to)
Because the flood has made the brige inaccessible to automobiles and pedestrains alike, we had rented a small boat to reach the island.
前面交代借船的原因了，所以借船必须是we have to rent
因果
两个idea有因果关系时，不能用with引导什么从句，必须要用because连接两个句子
With billions of tons yet to be mined, some aurgue that coal conservation measures are unnecessary.
表示清楚因果关系，改为because billions of tons of coal are yet to be mined
注意表示因果关系的词because优先＞because优先＞with…being…having…by…阿猫…阿狗…
当然鉴于because of有时候可以形成名词并列，有时候可以由于because.
对比和相反（有待验证！！！）
两者是有区别的！对比的话，对比双方的对应属性都会被提到。而相反（不像A，B怎么怎么），则A的对应属性不会被提到，B的会被提到。
Contrasting with most other fifteenth-century rulers, Portuguese kings could count on the support of the aristocracy in any overseas ventures.
改为unlike.看不出具体对比的东西是吧？


此句甚欠。”fish”是复数所以用”were.” 然后又蹦出来个” each of them”所以后面的”its”是对的。
13. Someone living in a technological, consumption-oriented culture probably taxes the environment at a rate many times that of a country such as Myanmar.
(换成that of someone living in a country like Myanmar.)看整个句子，主语应该是：Someone. 按理说应该是that of someone.
14. Before Homecoming Weekend, Lucia and Kiki took time to study for the upcoming finals, but as a result of the game and many parties, she needed to study again.
前面提到了两个女生，所以she属于无法指代明确，要改成具体的人名。
“A of B”指代的是A还是B
15. The number of awards given this year to biochemists accentuate the sigmificant gains being made in the study of the chemistry of living oragnisms.
“accentuate”指代的是”the number”！所以是”accentuates”。
句子所介绍的对象在句子中变着法出现。。。一定要一致
16. The second-year students at this college have evolved into insightful, critical thinkers from an inexperienced and uncertain teenager just a year before.
“Teenager”的出现。。。很不显眼。其实teenager指的就是students。所以只要选项中是”teenagers”就万事大吉。。。（选项很迷惑。。。。: From the inexperienced and uncertain teenagers they were just a year ago）
指代词前有一些成分。。。（注意：the number of时后面的动词一定是单数）
17. Most major air pollutants cannot be seen, although large amounts of them concentrated in cities are visible as smog. (No error)
Them没错，因为前面说的是pollutants。Are也没错，因为前面是a large amounts。
18. Though Rivers had done all the work, Peters had taken all the credit, and so he held him in contempt.
He held him完全指代模糊，错
指代的是复数，that要变those
19. Annual visitors to New York City’s Central Park number almost ten times that of Munt Rushmore.
先分析句子：主语：Annual visitors
动词：Number
所以that应该是those
②动词发出者是谁
1. While visiting my grandparents in Amsterdam, I saw an impressive model of the Rotterdam library roaming through the various exhibits at the Madurodam. （如此多dam）
非谓语动词roaming紧跟着Rotterdam library，但library不能roaming！应该是I roaming才对。多因该改改为while I am roaming。
2. As the guide led us through the exhibit of ancient Russian icons, she interspersed explanation of the object with stories about her own first encounters with Russian art, giving you a unique personal dimension to the tour.
虽然非谓语动词(giving)的发出者应该跟主句主语一致，但这里如果换就近原则解释的话，又可以以Russian art作发出者。所以错。
3. The historian argued that we ought to learn more about the process by which individuals like Sam Houston were identified by others as leaders.
这句话没错。因为like Sam Honston相当于插入语；既然从句的主语是individuals，那么动词就应该是were.
五、where/when/which/that/in which/by which/… 使用问题


六、叠加后的词义矛盾或重复
矛盾：1. Carmen Smith’s novel Hope sheds light on the character Anita, who as a young woman has scarcely no memory of her own upbring.
Scarcely和no叠在一起意思矛盾：不能说几乎不。要么no要么scarcely
重复：2. A volunteer organization, the CSK has been feeding needy family since 1977, annually distributing nearly a million pounds of food each year.
Each year等于annually，所以不需要each year了。
3. B simultaneously listened to music and did homework at the same time.
。。。
比较级重复4.If properly cared for, a hundred-year-old violin will produce a more fuller sound than it did when it was first used. (a fuller sound)
七、可合并成比较级
1. She is more well suited to a career in the sciences.
合并成better
八、虚拟语气时用were
Before the curtain rose, A wished that he were back in bed.
九、其它：
fewer & less前者用于可数后者用于不可数！
Be under对，但be underneath不对。
Speculation 本身不能say anything。所以speculation后面不能加saying. 但可以加that引导的定语从句（充当形容词）以表示speculation的内容： There is speculation that the name “Wendy” was the invention of J.M. B.
Have sb do sth使某人做 you cannot expect to treat your friends badly and have no one notice
Have sth done 做完某事
易混的表示因果关系的逻辑词：Because, since, in that
十、副词修饰动词
Althoug the latest senatorial debate focused on the more controversial topics in the campaigh, the candidates conducted themselves much more civil than they had previously.
Civil应该是civilly。Conduct也不是“表现得”的意思。
从简(wordiness)
最好不要有被动语态
→名词
1. Although the politician was initially very sensitive to be criticized by the press, he quickly became more confident about responding to reporters’ sometimes pointed questions.
直接说”criticism”好了。。。
→主动语态
2. Set in the sicteenth century, the contemporary opera Galileo, Galilei was written by Philip Glass and enjoyed by modern audiences.
（注意Galileo, Galilei中间的”,”是分割名字用的）
首先应该说”was enjoyed by modern audiences”就是啰嗦。被动改为主动，可以说：G,G has enjoyed success with modern audiences.
还有，written by PG如果换成PG’s也没有问题。
所以最简结果就是PG’s contemporary opera G,G has enjoyed (great) success with modern audiences.
追求简单句
3. Once American films looked slick and commercial compared to European imports; now, almost the reverse is true.
“the reverse if true”几乎是不能再简单的句子了。而迷惑选项：it has now been almost reversed就太复杂了。。。
Because of最好变成because（一般表示因果关系的词都换成because或者since）。除非要追求名词平行。注意（在美国）最好不要用for表示英国关系，虽然也有例外。
能没从句就没从句
4. She was concerned about how Hank would react to the incident, but in searching his face, he did not seem to be at all embarrassed or troubled.


直接改成 主a search of his face 谓showed 宾that he seemed not at all toubleed
意思上合理即可
5. When Dr. Jantos speaks, she does not attempt to impress her listeners with her speaking.
其实impress her listeners就够了，with her speaking是废话，可以删掉。
Whether→that(n.)
6. Whether the ancient Egyptian actually sailed or did not to South America remains uncertain.
“是否是。。。是不确定”是很啰嗦的。直接说“什么是不确定的”就行了。改成that引导的主语从句：That the ancient Egyptian actually sailed.
一些要记住的东西吧。。。把阅读要包括进去
修改句子，根据“拉丁文语法”，选项最好不要以preposition（in/of/with…）作为末单词。
Plus 直接排除！
Employing=utilizing=using
Who前面可能会有those。 Those who expect filmmakers to follow the original text exactly.
Wonder表示“惊奇”、“惊叹”，所以也可以等同于awe
注意用排除法，错误选项都很荒唐或者说的观点都一样。挑那个与众不同的。
修改文章合并句子时，要考虑合并为并列成分；这样可以使句子更清晰。 Eg. Relations are simpler because each country has only a few scientists on this isolated continent. Treaty clauses assure that the research there is nonmilitary.两句加起来想说明relations更加简单和其原因，所以可以改为：Relations are simpler because each country has only a few scientists on this isolated continent and also because treaty clauses assure that the research there is nonmilitary.
大难题啊！一般情况下就看他答案给出的是不是句子就行了。（主语，谓语，宾语，注意定语who which很迷惑）
合并句子，注意句子间的逻辑关系：谁是因谁是果！
句子很蹊跷但严格意义上没错的就是没错：
In Gee’s band, Alabama, traditionally made quilts are aired outdoors on sunny days, attracting local quilters who enjoy this display of one another’s creations.
选答案的时候，一定不要想对了写错了。。。
地铁对美国乡下人是个很恐怖的东西
表示“因为”不要说”for.”


膜拜

回复：6楼
contrasting with 的题应该是逻辑主语的问题，那个王不能自己比，是被别人比的，所以是contrasted with

这不是我写的么。。。。

Mark

The second-year students at this college have evolved into insightful, critical thinkers 【from an inexperienced and uncertian teenager just a year before.】这题，
可是前面不是已经有了谓语动词 have 了吗？后面加个they were？？

ao