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！

＂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）＂我还是想不通？？？？？