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Paragraph 5 supports the idea that the Galapagos island chain was able to become "one of the world's greatest showcases of evolution" primarily because of A. the richness of the volcanic soil of each of the islands in the chain B. the distance of the individual islands from each other and from the mainland C. the relativity long time it took for the islands to become covered by organisms D. the outdoor laboratories that scientists have built on the islands to study evolution