Given the task definition and input, reply with output. 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").

Fact1: Amphibians have a relatively complex circulatory system with a three-chambered heart., Fact2: Frogs have a three-chambered heart, consisting of two atria and a single ventricle., Question: What group of animals do frogs belong to? (A) four limbs (B) animals (C) fish (D) warm-blooded (E) reptiles (F) Amphibians (G) more abundant (H) mammals
F