Branch circuit conductors installed within ___________ of a ballast shall have an insulation temperature rating not lower than 90° C.

The correct response indicates that branch circuit conductors installed within 3 inches of a ballast must have an insulation temperature rating not lower than 90° C. This requirement is grounded in safety regulations and electrical code standards, which are designed to prevent overheating and ensure safe operation of electrical systems.

Conductors close to ballasts, such as those found in fluorescent lighting systems, can experience increased temperatures due to the ballast's function and electrical characteristics. If the conductors do not have a sufficiently high temperature rating, the heat generated can compromise the insulation, leading to failures, electrical shorts, or even fire hazards.

Understanding these specifications is crucial for anyone involved in electrical installations, as it emphasizes the importance of adhering to regulatory standards to maintain integrity and safety in electrical systems.