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 difference between water and ice results in ice floating on cold water?  
 (A) heat (B) shape (C) density (D) volume
Example Output: C

Example Input: When a hammer strikes a nail, the nail  
 (A) exerts balanced forces that helps it from moving. (B) exerts a force equal to the weight of the hammer. (C) exerts an unbalanced force that changes its velocity. (D) exerts an equal and opposite force back on the hammer.
Example Output: D

Example Input: Where would nitrogen most easily be found in the nitrogen cycle?  
 (A) in animal waste (B) in drinking water supplies (C) in underground mineral deposits (D) in carbon dioxide released by factories into the atmosphere
Example Output:
A