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:
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

Ex Output:
A

Ex Input:
Which of the following best describes an advantage of using a mass production manufacturing system instead of a custom manufacturing system?
(A) Customers can provide specific feedback to workers. (B) Workers become skilled in all aspects of assembly. (C) Goods can be easily modified for customers. (D) Products can be made at a lower cost.

Ex Output:
D

Ex Input:
What is the name of the process in which igneous, sedimentary, and metamorphic rocks are converted into one another in stages?
(A) rock cycle (B) erosion cycle (C) magma cycle (D) tectonic cycle

Ex Output:
A