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: Chordates have a complete digestive system and a closed circulatory system., Fact2: Chordates Chordates Chordates include fish, amphibians, reptiles, birds, and mammals., Question: What kind of circulatory system do fish have? (A) open (B) solid (C) closed (D) three (E) stagnant (F) kinetic (G) complex (H) gills
C