You are given a science question (hard-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.
Q: Roy's teacher asked him to identify a source of energy that is not easily replaced in nature. Which source of energy should Roy identify?  
 (A) coal (B) sunlight (C) water (D) wind
A: 
A