Which of the following pairs of substances illustrates the Law of Multiple Proportions?

Different proportions of oxygen in the various oxides of nitrogen prove the

$5.06 \ g$ of pure cupric oxide $(CuO)$ on complete reduction gives $4.04 \ g$ of metallic copper. In another experiment,$1.3 \ g$ of metallic copper is dissolved in nitric acid and the resulting solution is carefully dried to yield $1.63 \ g$ of $CuO$. Which law of chemical combination is illustrated by these results?

The law of definite proportions is not applicable to nitrogen oxides because

$45.4 \ L$ of dinitrogen reacts with $22.7 \ L$ of dioxygen to form $45.4 \ L$ of nitrous oxide. For the reaction $2N_{2(g)} + O_{2(g)} \to 2N_2O_{(g)}$,identify the law followed and state the law.

Identify the law for which the following statement is true.
"Equal volume of all gases at same temperature and pressure should contain equal number of molecules".