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 action involving a pulley system requires the least amount of force?  
 (A) using several pulleys together instead of a single pulley (B) using a fixed pulley instead of a moveable pulley (C) pulling a long rope instead of a short rope (D) pulling a rope up instead of down

A: A
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Q: In one area, a large source of prey for eagles is rabbits. If the number of rabbits suddenly decreases, what effect will it most likely have on the eagles?  
 (A) Their numbers will increase. (B) Their numbers will decrease. (C) They will adapt new behaviors. (D) They will migrate to new locations.

A: B
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Q: The element nitrogen can be found in simple, nonliving substances, such as air, and in complex molecules in living organisms, such as DNA. Which statement explains why nitrogen can exist in many compounds?  
 (A) Nitrogen atoms are different sizes. (B) Nitrogen atoms are different ages. (C) Nitrogen atoms can bond to different atoms. (D) Nitrogen atoms have different amounts of energy.

A:
C
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