Which statement correctly contrasts NM-B cable and THHN conductors?

• A. THHN are individual conductors used in conduit, rated for higher temperatures.
• B. NM-B is a sheathed, nonmetallic cable for dry indoor use; THHN are individual conductors used in conduit, rated for higher temperatures.
• C. NM-B conductors are rated for higher temperatures than THHN.
• D. THHN is a bundled cable for outdoor use.

Answer: (B)

Think about how they’re built and where they’re meant to be used. NM-B is a complete, sheathed nonmetallic cable containing several insulated conductors in one jacket, designed for dry indoor residential circuits and typically run in walls or concealed spaces. THHN conductors, on the other hand, are individual wires installed in conduit or other raceways; they’re not inside a single sheath. Because THHN insulation is rated for higher temperatures than NM-B, these individual conductors can carry more current in conduit, and they’re suitable for a broader range of environments, including higher-temperature situations. So the best statement highlights both the cable-versus-conductor distinction and the higher temperature rating of THHN. The other choices either omit the key difference, misstate how THHN is used, or claim NM-B has the higher temperature rating.