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 is the center of our solar system?  
 (A) Mars (B) The moon (C) Jupiter (D) The sun
[EX A]: D

[EX Q]: One substance found on Earth is more stable as an elemental gas than as part of a solid compound. As a result, this substance is very abundant in the atmosphere. Which substance exhibits these traits?  
 (A) argon (B) chlorine (C) nitrogen (D) oxygen
[EX A]: C

[EX Q]: Which trait most likely helps an animal survive in a very cold environment?  
 (A) long ears (B) large eyes (C) thick fur (D) sharp claws
[EX A]:
C