According to NFPA 70, which statement regarding underground cable and conductors is true?

The statement that insulated conductors and cables must be listed for use in wet locations is true according to NFPA 70. This standard emphasizes safety and reliability in electrical installations, particularly regarding the environmental conditions in which conductors will be installed.

Insulated cables that are used underground are exposed to moisture, soil, and potentially other environmental impacts. As such, selecting cables that are specifically rated and listed for wet locations ensures they can withstand these conditions without risk of failure or electrical hazards. This requirement not only promotes the longevity and functionality of the electrical system but also helps prevent accidents such as electrocution and short circuits, which can occur if inappropriate cables are used in environments with high moisture levels.

The other options do not align with safety standards as well as the correct choice does. For example, using uninsulated conductors in dry locations does not meet the stringent safety requirements for safeguarding against potential electrical issues. Similarly, the assertion that cables do not require any listing for underground use could lead to severe safety risks, as unlisted cables may not be designed for the specific hazards encountered underground. Lastly, the depth at which cables must be buried is often determined by local codes, but there isn't a blanket requirement of 5 feet for all underground installations.