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:
In an electric motor, electrical energy is converted into  
 (A) mechanical energy. (B) chemical energy. (C) thermal energy. (D) light energy.

Ex Output:
A


Ex Input:
During which stage of an insect's life cycle does the female lay eggs?  
 (A) nymph (B) larva (C) pupa (D) adult

Ex Output:
D


Ex 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

Ex Output:

D