You are given a science question (hard-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: A pot is touching the flame of a gas stove, and the substance in the pot is heating up due to the contact. This is an example of which type of energy transfer?  
 (A) radiation (B) convection (C) conduction (D) vaporization

A: C
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Q: Which substance is a compound?  
 (A) butter (B) nitrogen (C) hydrogen (D) ammonia

A: D
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Q: Which of the following is NOT a description of compounds?  
 (A) They can exist in the form of atoms or molecules. (B) They consist of atoms of two or more elements bonded together. (C) They have properties that are different from their component elements. (D) They can be broken down into elements by chemical means but not physical means.

A:
A
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