You are researching the conspiracy theory of the Kennedy assassination. You find a biography about the life of Lee Harvey Oswald. This source is:

A primary source

A secondary source

Secondary.

A biography is not written by the person, it is written by an author. This is secondary.

An autobiography is a biography written by that person. It is primary. This is not an autobiography, and so it is secondary.

A secondary source. A Biography is some one telling g someone else's story, while an Autobiography is like a really long memoir.