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:
All of the different organisms interacting in a pond make up  
 (A) a community (B) a population (C) the water cycle (D) the habitat

Ex Output:
A


Ex Input:
Which set contains kingdoms that contain only heterotrophs?   
 (A) Protists, Fungi (B) Bacteria, Animals (C) Plants, Fungi (D) Animals, Fungi

Ex Output:
D


Ex Input:
The burning of fossil fuels affects the atmosphere by  
 (A) adding more heat and carbon dioxide. (B) reducing the amount of necessary heat. (C) taking water vapor out of the atmosphere. (D) putting more oxygen in the atmosphere.

Ex Output:

A