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]: A scientist studies the remains of two extinct animals to learn more about how they lived. She determines that one animal was a carnivore and the other was an herbivore. Which of the following did the scientist most likely compare to make this conclusion?  
 (A) the number of bones in the animals (B) the size of the animals (C) the body covering of the animals (D) the skull of the animals
[EX A]: D

[EX Q]: What happens when water flows over a rock for a long period of time?  
 (A) erosion (B) flooding (C) breakage (D) evaporation
[EX A]: A

[EX Q]: If you breathe on a mirror, part of the mirror clouds up. What are you actually seeing when you see the mirror cloud up?  
 (A) Water droplets that formed from cooled water vapor in your breath (B) Carbon dioxide that you are breathing out from your lungs (C) Oxygen that you are breathing out from your lungs (D) Cooled nitrogen in the air around you
[EX A]:
A