Fittings and connectors must be used only with which of the following?

Fittings and connectors are crucial components in electrical installations, and they must be used solely with the wiring methods for which they are specifically designed and listed. This ensures that the components are compatible with the electrical and physical characteristics of the wiring method, which is essential for safety, reliability, and proper function.

When fittings and connectors are used as intended, they help maintain the integrity of the electrical system. They provide a secure and safe connection that can withstand environmental conditions and mechanical stresses, thus preventing issues like shorts or failures. Using components outside of their intended application could lead to hazards, such as overheating, fires, or circuit malfunctions.

The other options suggest a less appropriate use of fittings and connectors, either implying a lack of specificity regarding the type of wiring methods or suggesting outdated practices, which could compromise safety and code compliance.