According to MLA style, which of the following shows the correct capitalization for a book title?
 A. Parrots of the Wild: A natural history of the world's most captivating birds
 B. Parrots Of The Wild: A Natural History Of The World's Most Captivating Birds
 C. Parrots of the wild: a natural history of the world's most captivating birds
 D. Parrots of the Wild: A Natural History of the World's Most Captivating Birds