The correct option 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 neither created nor destroyed in a chemical reaction, so the total mass of reactants equals the total mass of products. However, the number of moles can vary depending on the coefficients in the balanced chemical equation.