The correct answer is D. Who
Step-by-step explanation:
A memoir is a narrative that tells or describes one striking or important personal experience. This narrative similar to others needs to include the who, what, when, why and where of the main event described. In the case of "who" this refers to the people and other entities that participated in the story who represent the characters. This means, in the case of Arnold his notes answer to "who?" because he has included mainly those that were part of his experience "Me, my dogs Daisy and Seamus", "my Dad, Can't remember if he was there", and even the creature he encountered "huge bear in the woods" that is also a character in the narrative.