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.

Ex Input:
The Grand Canyon is an example of  
 (A) erosion. (B) deposition. (C) an earthquake. (D) volcanic activity.

Ex Output:
A


Ex Input:
Which of the following is the best example of potential energy?  
 (A) a fallen rock (B) a burning match (C) a liter of gasoline (D) a red-hot piece of iron

Ex Output:
C


Ex Input:
Which of these cell structures converts nutrients to energy for cell functions?  
 (A) cell membrane (B) chloroplasts (C) mitochondria (D) endoplasmic reticulum

Ex Output:

C