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: One important use of coal is to produce energy for homes. Coal can be burned and converted to  
 (A) wind energy. (B) nuclear energy. (C) electrical energy. (D) solar energy.
Example Output: C

Example Input: Compost piles have many parts, such as leaves, moisture, vegetables, and microorganisms. Which part of a compost pile breaks down materials and adds nutrients to the soil?  
 (A) leaves (B) moisture (C) vegetables (D) microorganisms
Example Output: D

Example Input: Which resource is considered nonrenewable?  
 (A) wind power (B) solar energy (C) moving water (D) fossil fuels
Example Output:
D