* Glass: Glass is an excellent insulator, meaning it is extremely poor at conducting electricity.
* Salt Water: Salt water is a good conductor of electricity. The dissolved salt ions allow for the flow of electrical charge.
* Copper: Copper is an excellent conductor of electricity. It's commonly used in wiring due to its high conductivity.
* Mercury: Mercury is a liquid metal and a very good conductor of electricity.
Therefore, the least conductive material out of those listed is glass.
