Two samples of lead oxide were separately reduced to metallic lead by heating in a current of hydrogen. The weight of lead from one oxide was half the weight of lead obtained from the other oxide. The data illustrates

Question

$(a)\;\text { Law of reciprocal proportions } \\ (b)\;\text{Law of constant proportions} \\(c)\;\text{Law of multiple proportions} \\(d)\;\text{Law of conservation of mass}$