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: What has occurred when bubbles form in a liquid that is being heated?  
 (A) Oxygen is absorbed from the air. (B) Heat is radiating in the liquid. (C) The boiling point has been reached. (D) Molecular stability in the liquid is increasing.
Example Output: C

Example Input: The most significant human-induced impact on Earth's atmosphere comes from the use of which energy resource?  
 (A) flowing water (B) fossil fuels (C) sunlight (D) winds
Example Output: B

Example Input: The leaves of a tree change color in the fall. This is an example of a tree  
 (A) completing its life cycle (B) preparing for migration (C) responding to its environment (D) beginning hibernation
Example Output:
C