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: If the solar system were used as a model of an atom, what would the Sun most likely represent?  
 (A) an ion (B) a nucleus (C) a neutron (D) an electron
Example Output: B

Example Input: In 1971, the bones of an extinct flying dinosaur were discovered. This kind of discovery helps everyone learn more about  
 (A) impact of humans on Earth. (B) effect of gravity on animals. (C) history of animal species on Earth. (D) likelihood that dinosaurs will reappear.
Example Output: C

Example Input: The motion of atoms and molecules in a substance is  
 (A) thermal energy. (B) chemical energy. (C) mechanical energy. (D) electromagnetic energy.
Example Output:
A