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]: Diamonds are sometimes used as the tips of drill bits. Which physical property of a diamond MOST likely makes it a good cutting tool?  
 (A) its electrical properties (B) its thermal properties (C) its hardness (D) its density
[A]: C


[Q]: Which of the following is the best example of potential energy?  
 (A) a fallen rock (B) a burning match (C) a liter of gasoline (D) a red-hot piece of iron
[A]: C


[Q]: Raquel fed a litter of five kittens an all-meat diet for two weeks and found that they gained an average of 15 ounces. She concluded that eating meat is the best way to help kittens grow. What should Raquel have done to make this a better experiment?  
 (A) tested five kittens on a non-meat diet also (B) weighed the kittens in grams (C) used only one kitten (D) tested dogs as well as cats
[A]:
A