question: Ancestors of hagfish are thought to have been the earliest what?
choices.text: Extensive bone growth unicellular organisms humans last stage before adulthood animals with backbones dinosaurs bacteria To survive in their environment
choices.label: A B C D E F G H
fact2: Vertebrates are animals with backbones.
combinedfact: Ancestors of hagfish are thought to have been the earliest animals with backbones.
formatted_question: Ancestors of hagfish are thought to have been the earliest what? (A) Extensive bone growth (B) unicellular organisms (C) humans (D) last stage before adulthood (E) animals with backbones (F) dinosaurs (G) bacteria (H) To survive in their environment