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:
During a biochemical reaction, pyruvate (C3H4O3) is converted into carbon dioxide (CO2) and water (H2O). In what cellular organelle does this biochemical reaction occur?  
 (A) nucleus (B) cytoplasm (C) mitochondria (D) endoplasmic reticulum

Ex Output:
C


Ex Input:
Helen is preparing a presentation about objects in the solar system. She includes facts about the order of the planets and their distances from the Sun. Which statement could she include in an accurate presentation?  
 (A) Mars is closer to the Sun than Earth. (B) Neptune is one light-year from the Sun. (C) Jupiter is farther from the Sun than Uranus. (D) Earth is one astronomical unit from the Sun.

Ex Output:
D


Ex Input:
After which event will primary succession most likely occur?  
 (A) thunderstorm (B) crop harvest (C) volcanic eruption (D) urban development

Ex Output:

C