答案：C
第一句
Across brown bears—omnivores with high dietary plasticity—there is wide variety in dietary mix, which may reflect genetics, local resource availability, or social learning (cubs stay with their mothers for two years or more).
核心：棕熊食性多样，可能由遗传、当地资源、社会学习（幼崽跟母亲生活两年或更久）影响。
作用：给出研究背景，为下文研究和发现做铺垫。
第二句
Evaluating these possibilities, Anne Hertel et al. analyzed 30 years of data on trophic position (indicative of dietary mix) for female brown bears.
核心：Hertel 等人分析 30 年雌性棕熊的营养级数据（反映食性构成）。
作用：说明研究设计——引入了trophic position的代理指标，来反应饮食构成。
第三&四句
After separation, daughters, who tended to settle near their mothers, occupied the same trophic positions as their mothers for two years, but the correlation disappeared by year five. Trophic correlation with unrelated individuals in similar habitats was modest, while habitat-independent correlation with nonmaternal relatives (e.g., cousins) was no different than with unrelated individuals.
核心：这两句话中有3个主要发现：
2. 与不相关的个体在相似栖息地中，食性相关性不大。
3. 与不共享栖息地的非直系亲属（如表亲）的食性相关性，和不相关的个体无差别。
作用：研究发现，需要和前文背景做对应
发现1（跟母亲在一起）对应social learning对饮食的影响；
发现2（相似栖息地）对应local resource availability对饮食的影响；
发现3（非直系亲属和相关个体）对应genetics对应饮食的影响。
A)
social learning and resource fluctuations may both play a role in dietary mix among females, at least temporarily, though genetic factors appear to make a significant contribution as well.
❌明显错误在though后半句，可以重点看下发现3，说明遗传因素没有显著贡献：表亲（共享部分遗传）若不共享栖息地，食性无相关→ 不支持遗传主导。当然前半句的表述也不够全面，因为resource对diet影响相对比较小。
B)
female dietary mix is best understood as changeable and contingent on fluctuating environmental conditions rather than as the result of social learning or genetic factors.
❌前两年母亲-女儿相关明显，说明社会学习有作用，不能完全排除。
C)
dietary mix among females may reflect a social learning effect that eventually diminishes, though environmental constraints cannot be ruled out as a contributing factor.
前两年跟妈妈在一起，吃的跟妈妈差不多→ 社会学习；五岁的时候，相似消失→ 社会学习效应消失。
环境约束不能排除”与文中“相似 habitat 有 modest correlation”一致。
D)
dietary similarity among female brown bears is likely driven primarily by social learning during early independence but fades quickly as individual foraging habits develop.
❌ 与 evidence 前半部分吻合。但 D 完全没提 habitat 的影响，但文中 modest correlation 与 habitat 相关，暗示不能完全排除环境因素。
表述太绝对，把“primarily driven by social learning”且完全归因于个体习惯发展，忽略了环境因素的可能贡献。
