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 form of energy is being used when a person pushes a wooden block across the floor?  
 (A) mechanical (B) magnetic (C) sound (D) electrical

Ex Output:
A


Ex Input:
Seismic waves occur as a result of an earthquake. Which statement describes a wave property that makes it possible for scientists to locate the source of an earthquake?  
 (A) The wavelength of a wave is measured from crest to crest. (B) Waves travel uniformly outward from the wave source. (C) The frequency of waves varies in different mediums. (D) Waves move at the same speed in different materials.

Ex Output:
B


Ex Input:
What is a primary role of decomposers in an ecosystem?  
 (A) They eliminate matter by taking nitrogen from the ecosystem. (B) They eliminate matter by taking phosphorus from the ecosystem. (C) They cycle matter by returning carbon and other matter to the ecosystem. (D) They cycle matter by returning oxygen and other matter to the ecosystem.

Ex Output:

C