A metal oxide is reduced by heating it in a stream of hydrogen. It is found that after complete reduction, 3.15 g of the oxide has yielded 1·05 g of the metal. We may deduce that
(a) the atomic weight of the metal is 8.
(b) the atomic weight of the metal is 4.
(c) the equivalent weight of the metal is 4.
(d) the equivalent weight of the metal is 8.