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: HIV infects and destroys helper T cells., Fact2: Because HIV attacks T cells, it essentially paralyzes the immune system., Question: what system does HIV attack? (A) complex (B) humans (C) infection (D) organ (E) brain (F) animals (G) spinal (H) immune
Output:
H