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
1. 修饰 ：(一级排除A,B,D, E ) 句末的分词逻辑主语考虑. 不定式不能单独在句末做修饰成分、 the participle protecting begins a phrase that explains what the shields did 句末分词短语的逻辑主语优先考虑句子的主语(最后一句显然是要修饰盾牌的，除了c之外，其他的都修饰不到这儿)。
2. 单复数 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. (单复数问题)
3. 词用法 a method of 正确，，， a method to / a method doing 不正确 a method of protecting would be more idiomatic than a method to protect in A or a method protecting in B
4. 同位语： 同位语要考虑是否逻辑意思内涵一致 a protection in D has no noun for which it can logically substitute.