Which of the Following Is True of a Chemical Reaction

Which of the following is true of a chemical reaction?

A) In a chemical reaction, the number of moles of product always equals the number of moles of reactants.
B) In a chemical reaction, the mass of the products always equals the mass of the starting materials that have reacted.
C) In a chemical reaction, the number of moles of product always equals the number of moles of reactants, and the mass of products always equals the mass of the starting materials that have reacted.
D) In a chemical reaction, the number of moles of product does not always equal the number of moles of reactants, and the mass of products does not always equal the mass of the starting materials that have reacted.