求助og39题，以前没有讨论过的！谢谢大家了！

39. For members of the seventeenth-century Ashanti nation in Africa, animal-hide shields with wooden frames were essential items of military equipment, a method to protect warriors against enemy arrows and spears.
(A) a method to protect
(B) as a method protecting
(C) protecting
(D) as a protection of
(E) to protect
Choice C is best because the participle protecting begins a phrase that explains what the shields did. Choices A and B awkwardly use the singular word method to refer to items of military equipment rather than to the use of such items. Also, a method of protecting would be more idiomatic than a method to protect in A or a method protecting in B. In B and D, as is incorrect; also, a protection in D has no noun for which it can logically substitute. Choice E is incomplete; used to protect would have been acceptable.

首先， a protection in D has no noun for which it can logically substitute. 不是很能理解？

另外，对于as，刚才查了“英语语法大全”，没有发现d中的as使用有什么不对，请教大家！

最后， a method of protecting would be more idiomatic than a method to protect in A or a method protecting in B.  为什么用动名词会好些，请教！

谢谢！

个人观点：1，a protection 不能替换shields 也不能替换items 而替换military equipment不合理

2，ets在gmat中as常作为连词，用以带出一个主谓结构，只带出一个名词经常被视为错；另外这里要表达一个东西的功能，好像不需要as……的结构出现，只有个别时候如：use A as B to do C 的时候 as的使用才比较合理

3 a method of doing要好于to do 和doing 这是ets明确告诉了我们他的喜好，我们似乎只需要熟记即可（我比较没有追求） 至于理由，等我们杀到美国以后当面质问ets去！

LDOCE：

method of/for (doing) something

e.g.：

1.Today’s methods of birth control make it possible for a couple to choose whether or not to have a child.

2.effective methods for the storage and retrieval of information

非常感谢lypwilliam 和 wwwhahchn ，但对于lypwilliam说的“1，a protection 不能替换shields 也不能替换items 而替换military equipment不合理”还是不能理解，a protection 为什么不能替代shields或者items或者military equipment。

先谢过了！

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

(E)   flourishing at the same time as those were

Choice A, the best answer， 刚发现的一道题，也是as＋n.

相当confuse啊！请教！

个人观点：ets非常讲究对应，单数a protectiion 应该是不能替代复数名词的 另外，上面这个可不是简单的as＋名词结构，应该看的稍微多一点，这是一个标准的：the same……as……结构呀！呵呵

其实我的理解也非常粗浅，如果完全不着调，还请见谅