Definition: 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").
Input: Fact1: Echinoderms lack respiratory and excretory systems., Fact2: Echinoderms are represented by the starfish., Question: What lacks respiratory and excretory systems? (A) the Sun (B) insects (C) starfish (D) barnacles (E) ferns (F) water (G) Conifers (H) humans
Output:
C