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: Which best describes a scientific theory?  
 (A) It is still being tested. (B) It is true, once written. (C) It is different for each continent. (D) It is determined in a court of law.
Example Output: A

Example Input: Photosynthesis is the process that converts carbon dioxide and water into  
 (A) carbon and oxygen. (B) sugar and hydrogen. (C) sugar and oxygen. (D) nitrogen and carbon.
Example Output: C

Example Input: A longitudinal wave, such as a sound wave, can travel through  
 (A) solids only. (B) liquids only. (C) gas, liquids, and solids. (D) gas and a vacuum only.
Example Output:
C