(N/A) Compounds having the same molecular formula but with different structures are called structural isomers. The given compounds have the same molecular formula but they differ in the position of the functional group (ketone group).
In structure $I$,the ketone group is at the $C-3$ of the parent chain (pentane chain) and in structure $II$,the ketone group is at the $C-2$ of the parent chain (pentane chain). Hence,the given pair represents structural isomers.
$(b)$ Compounds having the same molecular formula,the same constitution,and the sequence of covalent bonds,but with different relative positions of their atoms in space are called geometrical isomers.
In structures $I$ and $II$,the relative positions of Deuterium $(D)$ and hydrogen $(H)$ in space are different. Hence,the given pairs represent geometrical isomers.
$(c)$ The given structures are canonical structures or contributing structures. They are hypothetical and individually do not represent any real molecule. Hence,the given pair represents resonance structures.