Fact 1: Wiring requires an electrical conductor.

Fact 2: An insulator is the opposite of a conductor.

Given the two facts above, answer the question "What is absolutely required for wiring to work??" with the following options: 
- increases a body's strength
 - heat is produced
 - The opposite of an insulator.
 - Something that comes in a bundle of fibers
 - quart or nickel plated aluminum
 - To another location like underground
 - underground systems
 - Time and energy


 

   The opposite of an insulator.      