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: The nucleus of MOST atoms consists of  
 (A) neutrons only (B) protons and neutrons (C) protons and electrons (D) neutrons and electrons
Example Output: B

Example Input: A student placed a small chip of limestone into a hydrochloric acid solution, and carbon dioxide gas was released. The carbon dioxide provided evidence that   
 (A) only a physical change occurred. (B) a chemical change occurred. (C) only a loss of mass occurred. (D) the formation of an element occurred.
Example Output: B

Example Input: Which characteristic is shared by Earth and the Moon?  
 (A) glaciers (B) flowing water (C) an atmosphere that contains oxygen (D) an orbit created by the force of gravity
Example Output:
D