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.

Which force produces energy as heat?  
 (A) pull (B) gravity (C) friction (D) magnetic
C

Because copper is a metal, it is  
 (A) liquid at room temperature (B) nonreactive with other substances (C) a poor conductor of electricity (D) a good conductor of heat
D

On a warm sunny afternoon, ocean water splashed onto a rock. A short time later, the rock was dry. Which statement best explains what happened to the water on the rock?  
 (A) Heat caused the water to become a gas. (B) Heat melted the water and it disappeared. (C) Salt caused the water to become a gas. (D) Salt melted the water and it disappeared.

A