How would you designate a cable that contains two No. 12 wires and a grounding wire?

The designation of a cable typically follows a specific format that indicates the gauge of the conductors and the number of wires included. In this case, the correct answer uses the format that specifies two No. 12 wires along with a grounding wire.

The "12" in the designation refers to the wire gauge, which is 12 AWG (American Wire Gauge); this is a standard way to describe the size of electrical wire. The "2" indicates that there are two insulated conductors of that gauge. The “w/g” at the end signifies that there is also a grounding wire included in the cable.

This method of denoting cable effectively communicates not only the number and size of conductors but also the presence of a grounding wire, which is essential for safety in electrical installations. Understanding this format is crucial for ensuring the correct type of wire is used in various electrical applications. Other choices do not conform to this standardized naming convention, making them unsuitable for describing a cable with two No. 12 wires and a grounding wire.