Who proposed the Law of Multiple Proportions?

To check the principle of multiple proportions,a series of pure binary compounds $(P_m Q_n)$ were analyzed and their composition is tabulated below. The correct option$(s)$ is(are)

Compound	Weight $\%$ of $P$	Weight $\%$ of $Q$
$1$	$50$	$50$
$2$	$44.4$	$55.6$
$3$	$40$	$60$

$(A)$ If empirical formula of compound $3$ is $P_3 Q_4$,then the empirical formula of compound $2$ is $P_3 Q_5$.
$(B)$ If empirical formula of compound $3$ is $P_3 Q_2$ and atomic weight of element $P$ is $20$,then the atomic weight of $Q$ is $45$.
$(C)$ If empirical formula of compound $2$ is $PQ$,then the empirical formula of the compound $1$ is $P_5 Q_4$.
$(D)$ If atomic weight of $P$ and $Q$ are $70$ and $35$,respectively,then the empirical formula of compound $1$ is $P_2 Q$.

When the volume is expressed,what does the law of definite proportions represent?

When $2.16 \ g$ of metallic copper is treated with nitric acid,the weight of copper oxide obtained is $2.70 \ g$. In a second experiment,$1.15 \ g$ of copper oxide on reduction gives $0.92 \ g$ of copper. These results illustrate the law of:

When $0.32 \ g$ of sulfur is burnt in air,$224 \ mL$ of $SO_2$ is obtained at $N.T.P$. In another experiment,$SO_2$ is formed by the decomposition of a compound containing $50\%$ sulfur. The results of the given information follow the law of ......

Reduction of $2.4 \ g$ of $FeO$ with hydrogen yields $1.68 \ g$ of $Fe$. In another experiment,$2.9 \ g$ of $FeO$ on reduction with hydrogen yields $2.03 \ g$ of $Fe$. These results illustrate the law of: