OG详解-OG8 文法 Q30

Choice D is the best answer. The sentence emphasizes the role a misconception played in the naming of a place, explaining that Spanish explorers mistook a peninsula for an island and, as a result, named the peninsula after a fictional island, California. 
Choice A is incorrect. The sentence mentions a novel that featured a fictional island, California; it doesn’t emphasize the role a misconception played in the naming of a place. Choice B is incorrect. The sentence notes that Baja California was originally named after a fictional place; it doesn’t emphasize the role a misconception—specifically, the Spanish explorers’ mistaken belief that the peninsula was an island—played in the naming of a place. Choice C is incorrect. The sentence indicates when Spanish explorers learned of the peninsula they called California; it doesn’t emphasize the role a misconception played in the naming of a place.