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]: Which is an example of a chemical reaction?  
 (A) Vinegar added to baking soda forms a gas. (B) Water evaporates into air. (C) Sugar dissolves in water. (D) Corn kernels are crushed to form flour.
[EX A]: A

[EX Q]: Divergent tectonic plate boundaries most commonly form  
 (A) ocean ridges. (B) ocean trenches. (C) non-volcanic islands. (D) continental mountains.
[EX A]: A

[EX Q]: The elements sulfur (S) and oxygen (O2) combine to form a substance called sulfur dioxide (SO2). Sulfur dioxide is also formed when coal and oil are burned. Sulfur dioxide can best be described as  
 (A) a metal (B) an atom (C) a compound (D) a nonreactive gas
[EX A]:
C