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.

Input: Consider Input: What is the main function of red blood cells?  
 (A) To fight disease in the body (B) To carry oxygen to all parts of the body (C) To remove carbon monoxide from all parts of the body (D) To produce materials which cause the blood to clot.

Output: B


Input: Consider Input: When do mutations help make an ecosystem more sustainable?  
 (A) when mutations decrease the number of individuals in an ecosystem (B) when mutations increase the number of individuals in an ecosystem (C) when mutations decrease the number of species in an ecosystem (D) when mutations increase the number of species in an ecosystem

Output: D


Input: Consider Input: Which two body systems would most directly remove extra fluid from a person's lungs?  
 (A) nervous and digestive (B) nervous and circulatory (C) respiratory and digestive (D) respiratory and circulatory


Output: D