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: In a northern state, a room used for growing plants is not allowing enough light to enter for healthy plant growth. Adding windows in walls facing which direction would best solve this problem?
(A) north (B) south (C) east (D) west
Example Output: B

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: Light enters the human eye through the
(A) retina. (B) pupil. (C) iris. (D) lens.
Example Output:
B