Read this paragraph. Ricardo dedicated his adult life to teaching the children of Five Pines Middle School. He taught Life Science for twenty-five years, and his lessons often extended into the marshes that surrounded the school. His classroom was always a lab in progress, and students made daily discoveries. In 1994, he began a modest adventure club to provide enriching experiences for his students. The club was an immediate success, and Ricardo received Five Pines’ Teacher Innovator Award that spring.

Why is this writing considered a biography?

A:because it tells an imagined story with unrealistic details
B:because it explains an important historical event
C:because it includes the author’s personal thoughts
D:because it contains researched facts about a person’s life