What is an example of a chemical reaction

One example of a chemical reaction is when pancake batter is fried or cake batter is baked. Basically it is a chemical reaction when a new substance is created by the change of another substance or thing. Clues of a chemical reaction is when a gas, bubbles, change of color, giving off of heat when changed, or when another substance or thing is created when that occurs. Another example is a fire. When a fire is on wood the wood burns therefore the wood turns into ash, another substance.

Ibelieve its a because an empirical formula usually has a ch in it your options are a or b