A + BC. When the reactant ABC is decomposed, it will produce the products A + BC. The equation should read ABC --> A + BC. 2AB+C would not be a balanced equation according to the law of conservation of mass since this would produce 2A, 2B, and C. Since the original reactant was ABC, this could not be balanced. AB + CD is incorrect as the element D was not an original reactant. This does not follow the law that matter cannot be created nor destroyed. B + C has a similar problem as element A drops out of the equation. Because A was a part of the reactant, it needs to be part of the product.