What are the materials that enter into a chemical reaction and are changed by it?
a) reactants
b)coefficients
c)solutes
d)products

In a chemical reaction, the atoms and molecules that interact with each other are called reactants. In a chemical reaction, the atoms and molecules produced by the reaction are called products.

Hope this helps.

Answer is A) reactants

They originally enter the chemical reaction and are changed by it, the products are a result of this procedure.

particle   p is an electron and particle q is a neutron