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.

Example Input: What determines how long the Moon takes to complete one cycle of phases?  
 (A) the period of rotation of the Moon around its axis (B) the period of revolution of the Moon around Earth (C) the period of rotation of Earth around its axis (D) the period of revolution of Earth around the Sun
Example Output: B

Example Input: A puppy has traits from its mother and its father. Which of these structures provides genetic information from the father to the puppy?  
 (A) a muscle cell (B) a nerve cell (C) a blood cell (D) a sperm cell
Example Output: D

Example Input: Which of the following is formed when two elements combine chemically?  
 (A) an atom (B) a compound (C) an electron (D) a mixture
Example Output:
B