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: Which form of energy are x rays and ultraviolet light?  
 (A) nuclear (B) heat (C) electromagnetic (D) chemical

A: C
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Q: Compost piles have many parts, such as leaves, moisture, vegetables, and microorganisms. Which part of a compost pile breaks down materials and adds nutrients to the soil?  
 (A) leaves (B) moisture (C) vegetables (D) microorganisms

A: D
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Q: When sugar is heated on a hot plate, it turns into a liquid. When the liquid sugar is cooled, a hard-crystalline substance is formed. This model best demonstrates the formation of  
 (A) molten rocks. (B) igneous rocks. (C) sedimentary rocks. (D) metamorphic rocks.

A:
B
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