Which of the following conductor arrangements is permitted by the NEC®?

To determine the correct answer regarding permitted conductor arrangements by the NEC® (National Electrical Code), it is important to identify the characteristics of the specified arrangements labeled as "a," "b," "c," and "d."

The National Electrical Code outlines specific guidelines concerning how conductors can be arranged to ensure safety, efficiency, and compliance with electrical standards. Conductors must be installed in a manner that prevents overheating, allows for proper dissipation of heat, and reduces the risk of short circuits and electrical faults.

The correct choice indicates that either arrangement "a" or "b" is permitted, suggesting that these particular configurations adhere to the NEC requirements. They likely follow protocols related to spacing, bundling limits, conductor types, and installation procedures defined in the code.

By contrast, arrangements "c" and "d" might not satisfy those requirements, perhaps due to reasons like insufficient separation between conductors, incorrect types of conductors being used together, or other potential hazards that could arise from those configurations.

Understanding the NEC’s stipulations is crucial for electrical professionals to ensure compliance with safety standards and to avoid penalties during inspections. Therefore, recognizing which arrangements are allowed is an essential part of electrical installation practices.