How frequently shall electrical wires be supported in an installation?

The correct answer reflects the industry standard for supporting electrical wires in an installation. Electrical wiring must be secured and supported to prevent sagging and potential damage. The requirement to support wires every 5 feet ensures that they are adequately maintained and mitigates the risk of mechanical stress on the insulation, which could lead to electrical failures or safety hazards.

Additionally, specifying support within 1 foot of a junction box or turn is critical because these locations are more vulnerable to movement and strain from connecting wires or bending. This ensures that wires are securely anchored in areas where they are likely to experience stress, preserving the integrity of the wiring system.

Standards such as these are designed to promote safety and reliability in electrical installations, which is why they are emphasized in relevant regulations and practices. Other options suggest different distances for support which either do not meet safety standards or are less practical for maintaining wire integrity.