Which section explains the differences between mandatory rules and permissive rules in the NEC?

The correct choice focuses on Section 90.5 of the National Electrical Code (NEC), which clearly delineates the distinctions between mandatory rules (requirements that must be followed) and permissive rules (preferences or suggestions that allow for options). This section outlines the significance of the wording used in the NEC, where mandatory rules are often indicated by terms like "shall" or "must," while permissive rules may use phrases such as "should" or "may." Understanding this distinction is crucial for compliance and safety in electrical installations.

In contrast, the other sections mentioned do not specifically address the differences between mandatory and permissive rules. Article 110 deals broadly with requirements for electrical installations, Section 90.3 covers the purpose and scope of the NEC, and Section 90.4 discusses the general requirements for applying the code. While those sections provide important context and information regarding the NEC, they do not focus on the distinction between types of rules as Section 90.5 does.