Answer:
Sentence 4) I did not know my small act of service would go down in history is from an autobiography.
Step-by-step explanation:
An autobiography is a self-written piece of writing that accounts of the life of oneself. In other words, it is the biography of oneself narrated by oneself. Therefore, sentences 1,2 and 3 cannot be from an autobiography because they are narrated in 3rd person. Sentence 4, on the other hand, meets the requiremets to be considered as part of an autobiography.