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 form of energy is being used when a person pushes a wooden block across the floor?  
 (A) mechanical (B) magnetic (C) sound (D) electrical

A: A
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Q: Which involves the greatest variety of cell types?  
 (A) a tissue (B) an organ (C) an organ system (D) an organism

A: D
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Q: A teacher asks her students to examine titles of four scientific articles. Which titled article is specifically about a chemical change?  
 (A) How Baking Soda Reacts With Vinegar (B) How Rust Can Be Scraped off of Metal (C) How Metals Respond to Electrical Currents (D) How Elements Can Change Phase When Heated

A:
A
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