Statement (A): In ${\mathrm{H}}_2{\mathrm{S}}_2{\mathrm{O}}_8$  , one peroxy linkage is present

 Statement (B): In organic compounds, carbon can have any oxidation number from −4 to +4 . 

Statement (C): Nitrogen exhibits more than three oxidation states.

The element carbon, C has four valence electrons it exhibits tetra valency of its compounds. Based on the nature of compound, the oxidation number of carbon varied from −4 to +4 . Nitrogen exhibits different oxidation states in its compounds. Ex: In NO, oxidation state of N is +2.

In ${\mathrm{NO}}_2$2 , oxidation state of N is +4 .In ${\mathrm{N}}_2\mathrm{O}$, the oxidation state of N is +1 . Similarly, in ${\mathrm{N}}_3\mathrm{H}$,the oxidation state of N is $-\frac{1}{3}$. In ${\mathrm{N}}_2{\mathrm{O}}_5$ , the oxidation state of N is +5 .

So, nitrogen exhibits more than three oxidation states in its compounds.

The structure of ${\mathrm{H}}_2{\mathrm{S}}_2{\mathrm{O}}_8$ is as follows: