I believe it would be to inform, the particular excerpt isn't really informing about anything, and its not persuading the reader to do anything, simply attempting to entertain the reader with a story.
Muir's writing is on both the beauty and harshness of nature. He talks about the beauty of the flower he discovered, but then talks about having to go without supper or blankets and how storms and the harsh weather conditions became welcomed after probably showing up a lot.
The answer is:
A.
Hope I could help ya ;)
