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.

[Q]: What is a decomposer?  
 (A) a living thing that breaks down dead organisms (B) a living thing that makes its own food (C) an animal that eats live plants (D) an animal that hunts other animals
[A]: A


[Q]: Which energy source is nonrenewable?  
 (A) sunlight (B) biomass (C) wind (D) fossil fuel
[A]: D


[Q]: The sound heard when a piano key is hit is caused by  
 (A) vibration. (B) refraction. (C) momentum. (D) acceleration.
[A]:
A