The author discusses Mayr, Ehrlich and Raven to demonstrate that
Explanation:
The scientists are in debate with each other over the fact that speciation occurs when species are isolated from each other. Mayr concluded in the first paragraph of the passage that when populations are isolated, speciation occurs. But Ehrlich and Raven observe that even though Checkerspot butterflies lived in close proximity, they did not interact with each other. This leads to a debate between the scientists.
Hence, option (c).
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