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 two protein molecules are essential for muscle contraction and relaxation?  
 (A) actin and myosin (B) collagen and tubulin (C) hemoglobin and myoglobin (D) amylase and polymerase

Output: A


Input: Consider Input: In an accurate diagram of the solar system, which object would be shown closest to Earth?  
 (A) the Moon (B) the asteroid belt (C) Mars (D) Saturn

Output: A


Input: Consider Input: Which tool is used to measure the volume of a liquid?  
 (A) balance (B) ruler (C) thermometer (D) graduated cylinder


Output: D