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 of these cycles takes 24 hours?  
 (A) Earth rotating on its axis (B) Earth revolving around the Sun (C) the Moon rotating on its axis (D) the Moon revolving around Earth

A: A
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Q: Which of these elements is found in the greatest amount in organisms?  
 (A) carbon (B) iron (C) lead (D) neon

A: A
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Q: A scientist observes that both birds and snakes in the same ecosystem depend on the same mouse species as a food source. The relationship between the birds and the snakes is an example of  
 (A) predation. (B) mutualism. (C) competition. (D) commensalism.

A:
C
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