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 unit of measurement describes an object's length?  
 (A) meter (B) kilogram (C) liter (D) degree
Example Output: A

Example Input: Which energy source is considered nonrenewable?  
 (A) moving water (B) fossil fuel (C) wind (D) biomass
Example Output: B

Example Input: Which widely used energy sources are nonrenewable and also a source of greenhouse gas emissions?  
 (A) wind turbines (B) hydroelectric dams (C) fossil fuels (D) solar cells
Example Output:
C