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 Q]: Which of these elements is found in the greatest amount in organisms?  
 (A) carbon (B) iron (C) lead (D) neon
[EX A]: A

[EX Q]: Water vapor sometimes condenses into stratus clouds that are in contact with the ground. What forms as a result of this process?  
 (A) ozone (B) methane (C) fog (D) smoke
[EX A]: C

[EX Q]: Auroras occur where Earth's magnetosphere traps high-energy particles in which region of the atmosphere?  
 (A) troposphere (B) stratosphere (C) thermosphere (D) exosphere
[EX A]:
C