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.

Example 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
Example Output: D

Example Input: All of the different organisms interacting in a pond make up  
 (A) a community (B) a population (C) the water cycle (D) the habitat
Example Output: A

Example Input: Upwelling moves the water of the deep ocean to the ocean's surface. What else does upwelling move to the surface?  
 (A) fish (B) nutrients (C) phytoplankton (D) dissolved gases
Example Output:
B