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.

Input: Consider Input: Campers shouted toward a canyon wall. What characteristic of sound best explains why the campers heard an echo?  
 (A) Sound waves traveled slowly down the canyon. (B) Sound waves were absorbed by the canyon wall. (C) Sound waves reflected off the canyon wall. (D) Sound waves were refracted around the canyon.

Output: C


Input: Consider Input: Which type of organism is the best at fixing nitrogen?  
 (A) bacteria (B) fungi (C) protists (D) animals

Output: A


Input: Consider Input: What happens when the Sun's energy warms ocean water?  
 (A) The water collects. (B) The water evaporates. (C) The water condenses. (D) The water precipitates.


Output: B