instruction:
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.
question:
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.
answer:
B


question:
Compared to Earth, the Moon is  
 (A) drier. (B) larger. (C) heavier. (D) brighter.
answer:
A


question:
What is the source of the organic matter needed for most fertile soils?  
 (A) moving water (B) eroded sand (C) decaying plants (D) weathered bedrock
answer:

C