In a chemical reaction, the number of moles of the reactants A.
should always be equal to the number of moles of the products.
B.
depends on the amount of product that is formed.
C.
should never be equal to the number of moles of the products.
D.
may or may not be equal to the number of moles of the products.

may or may not be equal to the number of moles of the products.

Explanation:

A chemical reaction involves the interaction between reactants to yield products. The number of moles of reactants and products in the system depends on the stoichiometry of the reaction.

The balanced reaction equation shows us the number of moles of reactants and products involved in the reaction.

Hence, in the balanced chemical reaction equation; the number of moles of reactants may or may not be equal to the number of moles of the products.

yes the answer is total mass in unchanged   : )