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]: Prolonged exercise stimulates muscle cells to absorb sugar from the blood. This mechanism reduces stress placed on the body by signaling the body to produce
(A) insulin. (B) lipids. (C) hemoglobin. (D) hydrochloric acid.
[A]: A

[Q]: Two atoms of oxygen combine to form pure oxygen gas. What is the electrical charge of the O_{2} molecules?
(A) positive (B) negative (C) neutral (D) variable
[A]: C

[Q]: Earthquakes and volcanic eruptions occur both on land and in water. Earthquakes and volcanic eruptions most often occur
(A) near plate boundaries (B) on large pieces of land (C) in large bodies of water (D) in regions near the equator
[A]:
A