题目解析:
题干提问“除了犁之外,以下哪项可导致苏美尔农业生产力的大幅增加?”
定位第3段第3句 The plow was developed as irrigation agriculture assumed greater importance in Sumer, and the combined innovations increased agricultural yields dramatically.由 combined innovations 得知前半句提及的 plow 和 irrigation 均为 innovation,除去 plow 剩余 irrigation。
故选 A。