Final answer:
The quotation that best summarizes Kerry Dirk's main idea in 'Navigating Genres' is Option D.
Step-by-step explanation:
The quotation that best sums up Kerry Dirk's main idea or overall thesis in 'Navigating Genres' is option D: 'My purposes are to expand your definition of genre (or to introduce you to a definition for the first time) and to help you start thinking about how genres might apply to your own writing endeavors.'