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: What tool would be used to examine a fingerprint?  
 (A) a graduated cylinder (B) a hand lens (C) a pair of goggles (D) a thermometer
Example Output: B

Example Input: An example of an instinct is  
 (A) laughing at something funny. (B) dogs doing tricks when told. (C) doing your homework at the same time each day. (D) salmon returning to their birthplace to lay their eggs.
Example Output:
D