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 force produces energy as heat?  
 (A) pull (B) gravity (C) friction (D) magnetic

A: C
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Q: When the cardboard cone of a radio speaker vibrates, it produces a sound in the air around it. The cone produces this sound by transferring which of the following to the air around it?  
 (A) heat (B) current (C) wave motion (D) magnetic force

A: C
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Q: Pumice is formed when lava from a volcano cools. Which rock type is pumice?  
 (A) Gaseous rock (B) Igneous rock (C) Sedimentary rock (D) Metamorphic rock

A:
B
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