Answer:
(D). Both metallic and ionic compounds can conduct electricity when molten. However, only metallic compounds can conduct electricity in a solid state.
Explanation:
Metallic compound have the ability to conduct electricity. Since they are Metals they have loosely held electrons which can contribute to electricity conduction.
Ionic compound are brittle physically, ionic compound cannot conduct electricity while being in solid state as the ions are held strongly by electrostatic force of attraction, they can only conduct electricity while they are in molten or aqueous state. In molten state they are forming ions, and ions are free to move within the solution and therefore contribute to electricity conduction.