What is the law of conservation of mass? A. The total mass of materials present after a chemical reaction is the same as the total mass present before the reaction.
B. In a given compound, the relative numbers and kinds of atoms are constant
C. If two elements A and B combine to form more than one compound, the masses of B that can combine with a given mass of A are in the ratio of small whole numbers.
D. Each element is composed of extremely small particles called atoms.