求教一道语法II

alex

For members of the seventeenth-century Ashanti nation in Africa, animal-hide shields with wooden frames were essential items of military equipment, [U]a method to protect [/U]warriors against enemy arrows and spears.
A.
C. protecting

本题的正确答案为C，可以理解。可是A本身有什么错呢？

Louisa_xy

语法上，a method 是equipment的同位语，但是逻辑上不通。

oddyuibe

同意楼上的观点~

alex

我认为'a method'指代前面一句话，即’animal-hide shields with wooden frames were essential items of military equipment‘。
是否正确？