Final answer:
Plastic is not recognized as an electrical conductor by the Code in 310.106(B); instead, metals like aluminum, copper, and steel are used due to their superior conductivity.
Step-by-step explanation:
The material that is not recognized by the Code in 310.106(B) for electrical conductors is plastic.
Metals such as aluminum, copper, and steel are commonly used for electrical conductors due to their conduction properties, which are tied to the presence of free electrons allowing electricity to pass through easily.
Plastic, on the other hand, is a poor conductor of electricity and is more commonly used as an insulator in the construction of electrical cables and devices.