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: Light enters the eye through an opening called the pupil., Fact2: Light enters the eye through the pupil, and the pupil is made larger or smaller by the iris., Question: What makes the pupil change sizes? (A) electrically (B) sun's heat (C) sweating (D) It expands (E) The iris (F) nerves (G) environment (H) heat
Output:
E