题目解析:
题干提问“除以下哪个选项外,其余是苏美尔人缺少的”,建议先看完四个选项,再逐一对应文本。
定位第2段第2句The Sumerians lived in a treeless, lowland environment with fertile soils but no metal, little timber, and no semiprecious stones.
其中no metal可排除B,little timber可排除D,no
semiprecious stones可排除A。
再结合第4句Sumerian rulers controlled not only large grain surpluses可知C选项的grain不缺少。
故选C。