Here's why:
* Memoir: A memoir is a non-fiction work that focuses on a specific period or theme in the author's life. It often blends personal experiences with historical context and reflection. "The Way to Rainy Mountain" fits this definition, as Momaday recounts his journey to his Kiowa ancestors' sacred site and explores the history and culture of his people.
Let's look at the other options:
* Journal: A journal is a personal record of daily events, thoughts, and feelings. While "The Way to Rainy Mountain" has elements of personal reflection, it's not a daily record.
* Autobiography: An autobiography is a comprehensive account of the author's entire life. "The Way to Rainy Mountain" focuses on a specific theme and period, not the entirety of Momaday's life.
* Diary: A diary is a personal record of daily events, usually kept private. "The Way to Rainy Mountain" is a published work, not a private journal.