If one of the reactants in a reaction is Na2O, what is known about the products? A. There is not enough information to say anything about the products. B.The products will contain exactly 2 Na atoms and 1 O atom. C.The products will have no more than 2 Na atoms and 1 O atom. D.The products will have at least 2 Na atoms and 1 O atom.

D.The products will have at least 2 Na atoms and 1 O atom.

Conservation of mass states that  

In a closed system, the masses before and after the reaction are the same

So it can be concluded

So the number of atoms in reactants and products remains the same

Because one of the reactants in a reaction is Na₂O, so The products will have at least 2 Na atoms and 1 O atom.

it is the most commonly accepted one