大全164 885-11-16

          Because natural gas is composed mostly of methane, a simple hydrocarbon, vehicles powered by natural gas emit less of certain pollutants than the burning of gasoline or diesel fuel.

(A) less of certain pollutants than the burning of gasoline or diesel fuel

(B) fewer of certain pollutants than burning gasoline or diesel fuel do

(C) less of certain pollutants than gasoline or diesel fuel

(D) fewer of certain pollutants than does burning gasoline or diesel fuel（E）

(E) less of certain pollutants than those burning gasoline or diesel fuel

另开一贴主要是想讨论一下补出主语及do的问题。

B中可否看作是省略了vehicles？参见OG187

187. In one of the bloodiest battles of the Civil War, fought at Sharpsburg, Maryland, on September 17, 1862, four times as many Americans were killed as would later be killed on the beaches of Normandy during
D-Day.
(A) Americans were killed as
(B) Americans were killed than
(C) Americans were killed than those who
(D) more Americans were killed as there
(E) more Americans were killed as those who

有没有哪位NN可以总结一下

(1)。什么时候需要补出谓语(如这里的do)，什么时候不需要？

(2)。什么时候可以省略被比较的主语，什么时候不可以省？

简直被ETS给玩晕了。。。

不知道jnlvo的这个著作里是否说明了，先参考一下吧。

http://forum.chasedream.com/dispbbs.asp?boardID=23&ID=57755&page=2

不是NN，对你的第一个问题有一点心得，想跟大家探讨一下。

对于什么时候省略助动词，什么时候不省的问题，我看OG的时候总结了一下，基本上觉得是这样：省略之后，有时候会造成歧义，不知道句子保留的是从句的主语还是宾语，这种时候就一定不能省；反之，如果没有这种歧义，就可以省。比如：

224. Inuits of the Bering Sea were in isolation from contact with Europeans longer than Aleuts or Inuits of the North Pacific and northern Alaska.

(A) in isolation from contact with Europeans longer than

(B) isolated from contact with Europeans longer than

(C) in isolation from contact with Europeans longer than were

(D) isolated from contact with Europeans longer than were（D）

(E) in isolation and without contacts with Europeans longer than

The phrasing of the comparisons in choices A, B, and E is incomplete, so the comparisons are ambiguous: because longer than could be followed by either from or were, it is unclear whether Inuits of the Bering Sea were isolated from Europeans longer than from the other Native American groups, or whether they were isolated from Europeans longer than the other groups were

这就是一个比较典型的例子，than从句后可以补出为from Aleuts or Inuits of the North Pacific and northern Alaska——宾语, 也可补出为were Aleuts or Inuits of the North Pacific and northern Alaska——主语.两者意思大不相同。

相反，也有不会产生歧义，所以省略助动词的例子，一时找不到了，如果看到再贴上来。不知道对不对，请指正。

找到一个：

80.   Salt deposits and moisture threaten to destroy the Mohenjo-Daro excavation in Pakistan, the site of an ancient civilization that flourished at the same time as the civilizations in the Nile delta and the river valleys of the Tigris and Euphrates.

(A) that flourished at the same time as the civilizations

(B) that had flourished at the same time as had the civilizations

(C) that flourished at the same time those had

(D) flourishing at the same time as those did（A）

(E) flourishing at the same time as those were

因为flourish后面不带宾语，所以从句保留部分不可能误解为宾语，只能是主语，所以省略助动词。

这么好的咚咚我以前怎么不知道？先谢谢stoneren，再慢慢研究!