【求指点】but前后到底需不需要平行？

Vanaron

97.   (29753-!-item-!-188;#058&003991)

Industrialization and modernmethods of insect control have improved the standard of living around the globewhile at the same time they have introduced some 100,000 dangerous chemicalpollutants, having gone virtually unregulated since they were developedmore than 50 years ago.

(A) while at the same time theyhave introduced some 100,000 dangerous chemical pollutants, having

(B) while at the same timeintroducing some 100,000 dangerous chemical pollutants that have

(C) while they have introduced some100,000 dangerous chemical pollutants at the same time, which have

(D) but introducing some 100,000dangerous chemical pollutants at the same time that have

(E) but at the same timeintroducing some 100,000 dangerous chemical pollutants, having

答案选B

选项ACE可以很容易排除掉。但D选项 答案说but后面的introducing 和主句的have improved 不并列，所以排除。很有道理 是吧？可是问题来了……

下面再另一道题目 也是来自prep

Unlike many United States cities, where a river is no longer the focal point of urban life, the river in San Antonio winds through the middle of the business district, and the River Walk, or Paseo del Rio, is the city's most popular attraction.
(A) Unlike many United States cities, where a river is no longer the focal point of urban life, the river in San Antonio
(B) Unlike the river in many cities in the United States, which is no longer the focal point of urban life, in San Antonio the river
(C) Today the river in many cities in the United States is no longer the focal point of urban life,
unlike San Antonio, where it
(D) In few United States cities today, a river is the focal point of urban life, but the river in San
Antonio
(E) No longer do many cities in the United States have a river as the focal point of urban life, but in San Antonio the river

（GMAT偏好句首的否定倒装用法）
句子结构：No longer do many cities… have a river…, but… the river winds through…, and the
River…, is…
副词no longer置于句首，整句倒装。
考点：比较、逻辑表达
1) 比较-unlike，与like用法相同，比较对象要对等。
2) 逻辑表达，原句中的副词等修饰成分不能随意改变，尤其是带有否定意义的词，如本题中的no
longer，会使句意发生改变。
(A) unlike连接比较对象不平行，cities和river。
(B) which指代United States错误，应该指代river。
(C) unlike一般不置于句中，容易产生对比歧义；it指代错误，在逻辑上不能指代前面的river。
(D) 去掉no longer，把全部否定变成部分否定，改变了原句意思。
(E) 正确，but连接并列的分句，不需要形式上完全对等。

有点confused。。

but前后并列与否是不是可以这么理解：当在连接两个完整的句子的时候也已不对等，但连接的是非完整句的时候要求就变严格了呢？

ykelly123

连接非完整句子的时候主语一定要一致，该省的省，不该省的不能省。
lz前一题的but前后不平行。主要是因为如果把主语补进去，就变成industrialization and modern methods...have improved...BUT (industrialization and modern methods) introducing...
BUT后面缺少谓语，这个谓语不能省因为but前后的时态不一样，一个是have + v-ed，一个是-ing

连接完整句子的时候主语可以不同，但是要注意主谓宾要全，一般前面有逗号，结构不一定要绝对一致

ps. 非NN

Vanaron

嗯 谢谢回答~：）

vinica

连接非完整句子的时候主语一定要一致，该省的省，不该省的不能省。
lz前一题的but前后不平行。主要是因为如果把主语补进去，就变成industrialization and modern methods...have improved...BUT (industrialization and modern methods) introducing...
BUT后面缺少谓语，这个谓语不能省因为but前后的时态不一样，一个是have + v-ed，一个是-ing

连接完整句子的时候主语可以不同，但是要注意主谓宾要全，一般前面有逗号，结构不一定要绝对一致

ps. 非NN

-- by 会员 ykelly123 (2011/9/30 22:10:24)

可是为什么while后面也是加introducing就可以啊？谓语也没有啊？？求教......

DY567

C比较对象不一致也是很明显的错误，拿river和san antonio对比，错。