While sulphur dioxide and hydrogen peroxide can act as oxidising as well as reducing agents in their reactions,ozone and nitric acid act only as oxidants. Why?

$(a)$ In sulphur dioxide $(SO_{2})$,the oxidation number $(O.N.)$ of $S$ is $+4$ and the range of the $O.N.$ that $S$ can have is from $+6$ to $-2$. Therefore,$SO_{2}$ can act as an oxidising as well as a reducing agent.
$(b)$ In hydrogen peroxide $(H_{2}O_{2})$,the $O.N.$ of $O$ is $-1$ and the range of the $O.N.$ that $O$ can have is from $0$ to $-2$. Hence,$H_{2}O_{2}$ can act as an oxidising as well as a reducing agent.
$(c)$ In ozone $(O_{3})$,the $O.N.$ of $O$ is $0$ and the range of the $O.N.$ that $O$ can have is from $0$ to $-2$. Therefore,the $O.N.$ of $O$ can only decrease. Hence,$O_{3}$ acts only as an oxidant.
$(d)$ In nitric acid $(HNO_{3})$,the $O.N.$ of $N$ is $+5$ and the range of the $O.N.$ that $N$ can have is from $+5$ to $-3$. Therefore,the $O.N.$ of $N$ can only decrease. Hence,$HNO_{3}$ acts only as an oxidant.