The statement related to law of definite proportions is

Law of definite proportions, statement that every chemical compound contains fixed and constant proportions (by mass) of its constituent elements.

$\%$ of oxygen in ${\mathrm{H}}_2\mathrm{O}$ is constant irrespective of the source is according to law of definite proportions

The ratio of oxygen in ${\mathrm{H}}_2\mathrm{O}$ and ${\mathrm{H}}_2{\mathrm{O}}_2$ with respect to fixed mass of $\mathrm{Hydrogen}$ atom is a whole number is according to law of multiple proportions.

Equal volume of all gases at the same temperature and pressure should contain equal number of molecules is according to avogadro's law.

Matter can neither be created nor destroyed is according to law of conservation mass.