Answer: Option (1) is the correct answer.
Explanation:
An ionic compound is the compound which is composed of oppositely charged ions.
When an ionic compound is in a solid state, then oppositely charged ions are held together by strong electrostatic force of attraction. To break is force of attraction, high energy is required. That is why, ionic compounds do not conduct electricity as a solid.
Whereas in melted state, the ions are less tightly held and as a result they can move easily from one place to another. Also in melted state, ionic compounds act as strong electrolyte. Hence, they are able to conduct electricity.
On the other hand, molecular compounds are poor conductors of electricity and non-metals do not conduct electricity. Whereas a metal is a good conductor of electricity even in its solid state.
Thus, we can conclude that a substance that does not conduct electricity as a solid but does conduct electricity when melted is most likely classified as an ionic compound.