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: The systems of the human body work together. Which system works with the skeletal system by pulling on the bones to create movement?  
 (A) digestive (B) circulatory (C) muscular (D) nervous

Answer: C


Question: Insulin is a chemical that is released by the endocrine system to increase the absorption of glucose by the body's cells. After which activity would insulin levels in a healthy body increase?  
 (A) drinking water (B) taking a nap (C) swimming (D) eating

Answer:
D