Final answer:
The passage is a memoir because it focuses on a single significant experience of the writer's.
Step-by-step explanation:
The characteristic that most clearly shows that the passage is a memoir is that it focuses on a single significant experience of the writer's. Memoirs typically center around a specific event or period of time in the author's life. In this case, the passage reflects on the writer's experiences through a personal lens, which is a key element of memoir writing.