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.

[EX Q]: The Grand Canyon is an example of  
 (A) erosion. (B) deposition. (C) an earthquake. (D) volcanic activity.
[EX A]: A

[EX Q]: Alex looked at an electric toothbrush that had a plug with three metal prongs. Why are these prongs made out of metal?  
 (A) Metal doesn't get hot and melt when you plug it into the outlet. (B) Metal is strong and is less likely to break when you plug it into the outlet. (C) Metal is an insulator and prevents shocks when you plug it into the outlet. (D) Metal is a conductor and completes a circuit when you plug it into the outlet.
[EX A]: D

[EX Q]: Which of the following is one reason that quartz is classified as a mineral?  
 (A) It can be manufactured. (B) It comes in different colors. (C) It has a specific crystal structure. (D) It can be melted at high temperatures.
[EX A]:
C