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: What force pulls things towards the center of Earth?  
 (A) magnetism (B) gravity (C) friction (D) energy

A: B
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Q: Which of these occurs if myosin fails to bind to actin during muscle contraction?  
 (A) The muscle cells will lose ATP. (B) The muscle cells will remain relaxed. (C) The muscle cells will produce lactic acid. (D) The muscle cells will lose calcium ions.

A: B
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Q: Which substance is composed of only one type of atom?  
 (A) water (B) gold (C) salt (D) sugar

A:
B
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