Instructions: 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: Starfish and sea urchins are also echinoderms., Question: what lack respiratory and excretory systems? (A) fish (B) graptolites (C) starfish (D) waste (E) humans (F) barnacles (G) insects (H) ferns
Output:
C