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
同位语短语可以提炼前面的句子或动作, 不一定非得指代前面的名词啊, 如此说来答案A如果改成a method of protecting应该是可以的吧. 请NN帮助确认一下. BTW, 我怎么记得method to do是正好的搭配呢. | 
