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: A star is a large astronomical body that  
 (A) reflects light. (B) condenses light. (C) emits light. (D) absorbs light.
Example Output: C

Example Input: Twentieth-century research and development of vaccines significantly reduced the threat of  
 (A) polio. (B) stroke. (C) diabetes. (D) osteoporosis.
Example Output:
A