You are given a science question (easy-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.

Input: Consider Input: Which characteristic best identifies a pure substance?
(A) shape (B) texture (C) melting point (D) state of matter

Output: C

Input: Consider Input: The human immunodeficiency virus (HIV) causes AIDS. The first known human cases AIDS were in Africa in the late 1950s. Since then, tens of millions of people have died from the disease, and tens of millions more people all over the world are infected. Which term best describes the disease AIDS?
(A) isolated cases (B) outbreak (C) epidemic (D) pandemic

Output: D

Input: Consider Input: Which is a reason for Arkansas having multiple seasons?
(A) the tilt of Earth's axis (B) the speed of Earth's orbit (C) Earth's distance from the Sun (D) Earth gravitational pull toward the Moon
Output: A