In this task, you are given two facts, and a multiple-choice question. Based on the given facts, answer the question with index of the correct option (e.g, "A").
Q: Fact1: Ancestors of hagfish are thought to have been the earliest vertebrates., Fact2: Hagfish and sharks are both isosmotic with their saline environments., Question: what are sharks? (A) vertebrates (B) bears (C) cold blooded (D) reptile (E) whales (F) their young (G) coelenterates (H) saves lives
A:
A