Each of the following models represents particles present before and after a chemical reaction which correctly shows conservation of mass during a
reaction?

D

Explanation:

According to the law of conservation of mass, matter can neither be created nor destroyed. The implication of this is that the total mass of reactants should be equal to the total mass of products.

There should be equal masses of reactants and products on both sides of the reaction equation. This most important condition is only satisfied by option D.

c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.