Hydrogen peroxide in its reaction with ${\mathrm{KIO}}_4$ and ${\mathrm{NH}}_2\mathrm{OH}$ respectively, is acting as a :

Hydrogen peroxide is clearly operating as a reducing and an oxidizing agent.

${\mathrm{KIO}}_4+{\mathrm{H}}_2{\mathrm{O}}_2\to {\mathrm{KIO}}_3+{\mathrm{H}}_2\mathrm{O}+{\mathrm{O}}_2$

${\mathrm{NH}}_2\mathrm{OH}+3{\mathrm{H}}_2{\mathrm{O}}_2\to {\mathrm{HNO}}_3+4{\mathrm{H}}_2\mathrm{O}$

Hence, ${\mathrm{KIO}}_4$ and ${\mathrm{NH}}_2\mathrm{OH}$ are reducing and oxidizing agent respectively.

So, option A is correct.