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 systems of the human body work together. Which system works with the skeletal system by pulling on the bones to create movement?  
 (A) digestive (B) circulatory (C) muscular (D) nervous
Example Output: C

Example Input: Which human organ system eliminates liquid and gaseous wastes from the body?  
 (A) circulatory (B) endocrine (C) excretory (D) reproductive
Example Output: C

Example Input: In an effort to preserve wildlife on his farm in Massachusetts, a farmer decides to stop using a 10-acre field. The farmer fences off the area, stops cutting the grass, and stops allowing livestock to graze on it. After twenty years, the area would most likely  
 (A) be covered with moss and rocks. (B) be a mature hardwood forest. (C) be grown over with bushes and small trees. (D) be barren due to lack of maintenance.
Example Output:
C