Passage Summary: Two neighboring groups share a unique building style that no one else around them uses, so the historian thinks one must have influenced the other.

Conclusion: The Swahili civilization was likely influenced by the Oromo culture to some degree.

Reasoning: Both groups share a specific architectural style—tombs with pillars and paneled facades—that is not found among any other groups the Swahili interacted with.

Analysis: The historian observes a correlation and immediately jumps to a specific direction of cause and effect. While it is possible the Oromo influenced the Swahili, the argument fails to consider that the influence could have gone the other way, or that both groups were influenced by a third, undiscovered culture. When you see a 'this indicates' claim based on a shared trait, always ask if the author has the direction of influence backwards. Look for an answer choice that points out this failure to consider alternative directions of influence.