The correct option that describes the reactants and products of a chemical reaction is:
The mass of the reactants must be equal to the mass of the products. The total number of moles of the reactants can be more or less than the total number of moles of the products.
This statement aligns with the law of conservation of mass, which states that mass is conserved in a closed system during a chemical reaction, whereas the number of moles can differ due to different molecular compositions in the reactants and products.