Cables or raceways installed using directional boring equipment shall be ______ for this purpose.

The correct answer is that cables or raceways installed using directional boring equipment must be "approved" for this purpose. This requirement ensures that the materials used are recognized and validated by relevant testing or certification organizations, signifying that they meet specific safety and quality standards necessary for underground installation.

The approval process often involves rigorous testing to determine how well the materials perform under various conditions, such as pressure, moisture, and chemical exposure. This step is essential, particularly for installations that may be subject to physical stress and environmental factors that could otherwise compromise their integrity and safety over time.

Understanding that the installation method, like directional boring, poses unique challenges is important. The materials must not only comply with general electrical codes but also with specific conditions associated with being buried underground where accessibility for future maintenance is limited. Approved materials help ensure that these installations will perform effectively and safely throughout their intended lifespan.