Context: This passage describes a chemical reaction. Read the passage. Then, follow the instructions below.
Hydrogen peroxide, a household disinfectant, breaks down into water and oxygen gas over time. Light speeds up this process, so hydrogen peroxide is typically stored in a dark-colored bottle. The bottle's dark coloring blocks light and makes the hydrogen peroxide last longer.
Complete the sentence.
In this chemical reaction, oxygen is a ().
A. product
B. reactant
Identify the correct option from the choices provided and respond with the letter of the correct option.

A