In which substance does nitrogen exhibit the lowest oxidation state?

In which of the following compounds,does nitrogen exhibit the highest oxidation state?

Sulphur has the highest oxidation state in

The equivalent weight of $K_{2}Cr_{2}O_{7}$ in acidic medium is expressed in terms of its molecular weight $(M)$ as

The oxidation state of the oxygen atom in potassium superoxide is:

Consider the following compounds:
$\underline{K}O_2$,$H_2\underline{O}_2$ and $H_2\underline{S}O_4$.
The oxidation states of the underlined elements in them are,respectively,