Phosphorus acid on heating gives the following products
$4{\mathrm{H}}_3\mathrm{P}{\mathrm{O}}_3\stackrel{\mathrm{\Delta }}{\to }3{\mathrm{H}}_3\mathrm{P}{\mathrm{O}}_4+\mathrm{P}{\mathrm{H}}_3$
The above reaction is an example of

In which one of the following sets all species show disproportionation reaction?

Which of the following reactions are disproportionation reaction?

$\left(a\right)$ $2\mathrm{C}{\mathrm{u}}^{+}\to \mathrm{C}{\mathrm{u}}^{2+}+\mathrm{C}{\mathrm{u}}^0$

$\left(b\right)$ $3\mathrm{M}\mathrm{n}{\mathrm{O}}_4^{2-}+4{\mathrm{H}}^{+}\to 2\mathrm{M}\mathrm{n}{\mathrm{O}}_4^{-}+\mathrm{M}\mathrm{n}{\mathrm{O}}_2+2{\mathrm{H}}_2\mathrm{O}$

$\left(c\right)$ $2\mathrm{K}\mathrm{M}\mathrm{n}{\mathrm{O}}_4\stackrel{∆}{\to }{\mathrm{K}}_2\mathrm{M}\mathrm{n}{\mathrm{O}}_4+\mathrm{M}\mathrm{n}{\mathrm{O}}_2+{\mathrm{O}}_2$

$\left(d\right)$ $2\mathrm{M}\mathrm{n}{\mathrm{O}}_4^{-}+3\mathrm{M}{\mathrm{n}}^{2+}+2{\mathrm{H}}_2\mathrm{O}\to 5\mathrm{M}\mathrm{n}{\mathrm{O}}_2+4{\mathrm{H}}^{\oplus }$

Select the correct option from the following:

Match List-I with List-II, match the gas evolved during each reaction.

Choose the correct answer from the options given below

Upon dipping a copper rod, the aqueous solution of the salt that can turn blue is: