19. (D)
Question Type: Synthesis (7, 23-31,48-50, 58-69)
The authors of these two passages do not have tunnel vision. Although both passages focus on the relationship of caries to the increased carbohydrate consumption that characterizes a move to a more agrarian lifestyle, both authors acknowledge that this is not a directly proportional relationship. Other factors influence the extent to which a population demonstrates caries. In paragraph one of Passage A, tooth structure is listed among the factors. In paragraph three of Passage A, the cariogenic properties of some gathered foods like plants and acorns are discussed. Passage B discusses the implication of tooth wear on caries in paragraph two, and in the final paragraph explains why the Thai population’s increased agrarianism didn’t ultimately result in a higher incidence of caries. We can conclude that neither author thinks that caries incidence corresponds directly to the degree of reliance on agriculture, proving (D) correct.
(A) is unsupported. Neither author says that populations predictably move towards agrarian lifestyles, so neither would say that caries rates increase predictably over time.
(B) is contradicted. Both authors rely on the accuracy of these records!
(C) is reversed.
(E) is unsupported. Both topics are discussed, but they are never compared.