Which of the following articles pertains to circuits operating at less than 50 volts?

The correct choice is based on the scope defined by the NEC for low-voltage circuits, specifically those operating at less than 50 volts. Article 720 covers "Circuits and Equipment Operating at Less Than 50 Volts," which includes a variety of special types of low-voltage systems used primarily for signaling, communications, and low-energy applications. This article outlines requirements and considerations for installations involving low-voltage circuits to ensure safety and functionality, emphasizing the significance of proper installation practices.

This choice reflects an understanding that certain electrical systems need specific guidelines separate from standard higher-voltage regulation, contributing to safer and more effective low-voltage system designs.