TASK DEFINITION: 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.
PROBLEM: In gym class a student kicks a soccer ball high into the air. As the ball goes upward, which type of energy is increasing?  
 (A) kinetic energy (B) thermal energy (C) potential energy (D) mechanical energy

SOLUTION: C

PROBLEM: Which of these is a nonliving part of a forest?  
 (A) Tree (B) Soil (C) Worm (D) Mushroom

SOLUTION: B

PROBLEM: When a guitar string is strummed, it produces sound by making  
 (A) heat. (B) electricity. (C) vibrations. (D) light.

SOLUTION:
C