Step-by-step explanation:
It is known that for electricity to pass through a substance it is important that the substance must have ions present in it.
This is because electricity is the flow of ions. So, when a substance is present in melted ionic form then it will have oppositely charged ions due to which electricity will be able to pass through it.
On the other hand, in a solid ionic compound there will be strong interaction between the ions. Hence, they are present in a lattice and not able to flow freely.
Therefore, a solid ionic compound is not able to conduct electricity.
Thus, we can conclude that out of the given options melted ionic compound is a better conductor of electric current.