In given question it is stated that 12 g of carbon react with 32 g of oxygen to produce carbon dioxide. The other combination option c is also true because in this, the quantity of both reactant is just half from the given quantity. Which means that if 100 % product is obtained from the 12 g of carbon and 32 g of oxygen then by taking the half amount of reactant the product will be half i.e 50% .
This combination is true because the ratio of both reactant are justified.
