The correct answer is D: The family was excited to visit the World's Largest Fish statue in Hayward and Mitchell's Corn Palace.
The sentence in option D follows the AP Style Guide rules of capitalization: World's Largest Fish (the three words are capitalized because they are part of a proper name) statue (this word is not part of the proper name.) Corn Palace (both words are part of a proper name, so they are capitalized.) Sentences B and C have cities that don't require the state names.