题目解析:
选项A对应倒数第二句的“have probably existed in most pastoralist societies”,符合原文,排除。
选项B对应倒数第二句“except in periods of military conquest, they are normally too slight to generate the stable”,即除了战乱时期,他们由于太过弱小难以形成通常的稳定、世袭的统治阶级,B选项说法符合原文,排除。
选项C对应“they are normally too slight to generate the stable, hereditary hierarchies”,因为太过弱小难以形成通常的稳定、世袭的统治阶级,选项中expressed说法与原文矛盾,正确。
选项 D对应“they are normally too slight to generate the stable, hereditary hierarchies that are usually implied by the use of the term class”,即因为平时不重要而不被讨论,选项与原文一致,排除。