Which of the following sentences violates correct capitalization rules?

The sentence in question violates correct capitalization rules due to the improper capitalization of "mouse." In this context, "Mickey Mouse" is a proper noun, referring to the well-known cartoon character created by Walt Disney. Proper nouns should always be capitalized. Since "Joe Camel" is also a proper noun, the sentence is inconsistent because it capitalizes one character's name correctly while failing to do so for the other.

The other sentences adhere to capitalization rules: the first correctly capitalizes "Martin Luther King," "I Have a Dream" (as the title of a speech), and "Washington, D.C.," while the second sentence correctly capitalizes "Derek Jeter" and "New York Yankees." The third sentence capitalizes "April," and "Six Flags Magic Mountain," both of which are proper nouns. Thus, while they maintain the correct rules of capitalization, sentence D fails to capitalize "mouse," which makes it the incorrect choice in terms of capitalization standards.