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: 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
Example Output: C

Example Input: Which characteristic best identifies a pure substance?  
 (A) shape (B) texture (C) melting point (D) state of matter
Example Output: C

Example Input: In an ecosystem, which list of organisms is in the correct order from producer to top-level consumer?  
 (A) field mouse, grass, hawk snake (B) snake, field mouse, hawk, grass (C) grass, field mouse, snake, hawk (D) snake, grass, field mouse, hawk
Example Output:
C