No markings on wires less than ____ inches.

• A. 1 inch
• B. 2 inches
• C. 4 inches
• D. 3 inches

Answer: (D)

Marking electrical wires so they can be identified quickly is essential for safety and maintenance. The standard calls for identification marks to be spaced along a wire at intervals no greater than 3 inches. That means every portion of a longer wire should have a mark within 3 inches of the next one, ensuring legibility even when routing or insulation is tight or damaged. If a wire segment is shorter than 3 inches, there isn’t enough room to place a readable mark, so there would be no markings on wires less than 3 inches. That’s why 3 inches is the correct threshold.