关于by doing 和 by n.的区别，请大牛们指教

gamxiaoyuan

The majority of scientists believe that to reduce and stabilize atmospheric concentrations of carbon dioxide, emissions must be cut at the source by fossil fuels that are burned more efficiently and, in some cases, by alternatives such as hydrogen fuel cells that can replace fossil fuels altogether.
(A) fossil fuels that are burned more efficiently and, in some cases, by alternatives such as hydrogen fuel cells that can replace fossil fuels altogether
(B) fossil fuels that are burned more efficiently and, in some cases, those that are replaced altogether with alternatives such as hydrogen fuel cells
(C) burning fossil fuels more efficiently and, in some cases, by replacing fossil fuels altogether with alternatives such as hydrogen fuel cells
(D) more efficiency in the burning of fossil fuels and, in some cases, by alternatives such as hydrogen fuel cells that can replace fossil fuels altogether
(E) the more efficient burning of fossil fuels and, in some cases, by fossil fuels that are replaced altogether with alternatives such as hydrogen fuel cells
这题选C，破解上说应该用by doing，但prep 32题破解又说“by doing 和by noun.都正确，但前者强调动作，后者强调结果，在GMAT语法中，通常by n.是正确的表达方式”——
32.The Chicago and Calumet Rivers originally flowed into the St. Lawrence by way of Lake Michigan, but having been redirected by constructing canals so that the water now empties into the Mississippi by way of the Illinois River.
(A) Rivers originally flowed into the St. Lawrence by way of Lake Michigan, but having been redirected by constructing  
(B) Rivers had originally flowed into the St. Lawrence by way of Lake Michigan, but they have been redirected by constructing
(C) Rivers, which originally flowed into the St. Lawrence by way of Lake Michigan but have been redirected by the construction of
(D) Rivers, originally flowing into the St. Lawrence by way of Lake Michigan, but having been redirected by the construction of  
(E) Rivers, originally flowing into the St. Lawrence by way of Lake Michigan, have been redirected through the construction of
哪位战友能给指点下？

gamxiaoyuan

没人回答？

sspooh

我不是大牛，不知道是否可以这样理解。
（1）看GMAT的语法后有一点不知是否正确的感悟，就是GMAT一般比较偏好于生动活泼的用词，比如动词。这里用by burning，by replacing，就好像活生生得正在烧，正在转移一样。
（2）AB选项中都有些被动语态的意思，C中的主动的意思要好过AB
（3）虽然GMAT偏好于使用by+n.，但是为了表达“通过做某事，使得......"这个意思，只有by doing才是正确的表达方法。前文说了，burning,replacing这样做的目的是为了to reduce and stabilize atmospheric......。
综上所述，个人觉得还是C好。

sspooh

顺便问一下楼主，32题选E么

sspooh

楼主......肿莫弃楼了......

gamxiaoyuan

32题是选E

sspooh

32题我是这么想的，不知道对不对
（1）having done永远不可以做后置定语修饰名词，因此AD错。
（2）一般情况下，若出现过去完成时，则必须有过去时与其相对应。OG-SC前面的语法规则中提到"this verb form is used with had to show the order of two events that took place in the past."。OG很多题目中前一个分句出现过去完成时，后一个分句必有过去时。因此B的过去时态不正确，感觉上缺少一个截止的时间。
（3）C中so that之前的分句没有main verb——fragments.
（4）E中句子结构：主语Rivers + 插入语originally + 谓语宾语+so that ......。谓语动词have been redirected......表示从过去某一时点开始建造，一直到now empties into M by way of I Rivers.