B-The body could break down proteins from muscles for energy.
Zirconium cannot be broken down by a chemical change, because it is an element. The others are all molecules.
In your choices, the best answer is the mass of the reactants and the mass of the products are no equal. The chemical equilibrium can take place in a close system and can not be affected by catalyst and is a reversible reaction. The best describe should be the concentration of reactants and products are constant.
