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:
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 Output:
D

Ex Input:
Which of the following units best represents the density of an object?
(A) kg (B) hr (C) m/s^2 (D) g/cm^3

Ex Output:
D

Ex Input:
Animal cells perform functions using energy that is derived from glucose (C6H12O6). Which molecule is required for animal cells to obtain the most energy possible from a molecule of glucose?
(A) water (B) oxygen (C) lactic acid (D) carbon dioxide

Ex Output:
B