What kind of wiring is typically used for inside feeder installations?

THHN (Thermoplastic High Heat-resistant Nylon-coated) is the correct choice for inside feeder installations due to its specifications and characteristics. This type of wiring is designed for use in dry locations, and it can handle a higher temperature rating, making it suitable for various applications in commercial and industrial settings. THHN wires are also known for their durability and resistance to moisture, which contributes to their widespread use in feeders inside buildings.

The other options, while useful in certain contexts, don't meet the same specifications for feeder installations. UF (Underground Feeder) is designed for direct burial or wet environments, making it more suited for outdoor applications. MC (Metal Clad) is often used in commercial buildings for its physical protection, but it is typically employed for branch circuit wiring rather than feeder applications. NM-C (Non-Metallic Sheathed Cable) is mostly intended for residential wiring in dry locations and not appropriate for feeder installations that require higher rating and capacity typically associated with THHN wiring.