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Question 51·Hard·Inferences

Residue analysis of 2,000-year-old ceramic cups from a desert archaeological site in what is now southern Arizona detected theobromine and caffeine, chemical markers uniquely associated with cacao beans. Botanical remains recovered from the same layers include seeds and pollen of drought-tolerant plants native to the region but none from cacao, a tree that today grows only in humid tropical areas of Mesoamerica and beyond. Given these findings, researchers argue that ____.

Which choice most logically completes the text?