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]: One of the main causes of acid rain is  
 (A) Waste from nuclear power plants (B) Spills from chemical manufacturing plants (C) Gases from burning fossil fuels (D) Gases from aerosol spray cans
[EX A]: C

[EX Q]: Which is the best example of something that has kinetic energy?  
 (A) a rock sitting at the top of a steep hill (B) a tennis ball rolling across the court (C) a picture hanging on the wall (D) a piece of wood before it is burned
[EX A]: B

[EX Q]: As wood in a campfire burns, it releases heat and becomes ash. What kind of change occurs in the wood when it burns and releases heat?  
 (A) nuclear (B) magnetic (C) chemical (D) mechanical
[EX A]:
C