A metal oxide is reduced by heating it in a stream of hydrogen. After complete reduction, it is found that $3\mathrm{.}15$ gm of the oxide has yielded $1\mathrm{.}05$ gm of the metal. It may be inferred that the

Atomic weight of the metal is $4$

Equivalent weight of the metal is $4$

Atomic weight of the metal is $2$

Equivalent weight of the metal is $8$