In a chemical reaction, water decomposes to form hydrogen and oxygen. what is the correct term for the water?
a. an element
b. an atom
c. a product
d. a reactant

In this case water is a reactant. In a chemical reaction one or more substances, reactants, are converted to one or more different substances, the products. The substances are either chemical elements or compounds. Chemical reactions reaction rearranges the constituent atoms of the reactants to create different substances as products. In this case water is the reactant while hydrogen and oxygen are the products.