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 the following compounds is most likely to be part of living organisms?  
 (A) C?H??O? (B) BF? (C) MoCl? (D) CsI
[EX A]: A

[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]: The heath hen, an extinct small wild fowl, was a relative of the prairie chicken. Which of the following most likely caused extinction of the heath hen?  
 (A) overhunting (B) stable climate (C) plentiful food supply (D) abundant nesting sites
[EX A]:
A