Consider the salt ${\mathrm{K}}_x{\mathrm{H}}_y{\left({\mathrm{C}}_2{\mathrm{O}}_4\right)}_z\cdot 2{\mathrm{H}}_2\mathrm{O}$ The relationship between x, y and z is:

Consider the salt,

${\mathrm{K}}_x{\mathrm{H}}_y{\left({\mathrm{C}}_2{\mathrm{O}}_4\right)}_z\cdot 2{\mathrm{H}}_2\mathrm{O}$

The oxidation number is shown as,

$\begin{array}{l}{K}_x^{+1}{H}_y^{+1}{\left({\mathrm{C}}_2{\mathrm{O}}_4^{-2}\right)}_{z}2{\mathrm{H}}_2\mathrm{O}\\ \to (+1)\times x+(+1)\times y-2\times z=0\\ \to x+y=2z\end{array}$

Hence, option B is correct.