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.
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Question: Two pieces of the same metal are placed on a table. The pieces of metal have the same density, mass, and texture. Which characteristic must be the ONLY difference between the two samples?  
 (A) They have different dimensions. (B) They have different boiling points. (C) They are made up of a different type of matter. (D) They contain a different amount of matter per unit volume.

Answer: A


Question: 22 Sandy is conducting an investigation to find out which food his dog likes best. Which is the manipulated variable in his investigation?  
 (A) The color of his dog's food dish (B) The kind of food he gives his dog (C) The amount of food he gives his dog (D) The time of day he feeds his dog

Answer: B


Question: Which of the following does not affect the strength of an electromagnet?  
 (A) number of times the wire is looped around the core (B) size of the object being attracted by the core (C) type of material in the core (D) amount of material in the core

Answer:
B