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: Arthropods are the largest phylum of invertebrates., Fact2: Invertebrates are animals without a backbone., Question: What don't arthropods have? (A) an exoskeleton (B) legs (C) Bodily water (D) Damaged hearing (E) kinetic energy (F) a backbone (G) Energy (H) backs
Output:
F