Which NAVAID transmits in VHF and provides horizontal guidance along the runway's extended centerline?

The localizer is a crucial component of the Instrument Landing System (ILS) that provides horizontal guidance to pilots during the landing phase. It transmits in the VHF band and helps ensure that an aircraft is aligned correctly with the runway's extended centerline. This alignment is essential for safe landings, especially in low visibility conditions.

When approaching the runway, the localizer signals guide the aircraft to maintain the correct path directly in line with the runway, allowing pilots to make precise adjustments as needed. The localizer operates on specific frequencies that fall within the VHF range, making it a vital aid for instrument approaches.

The other options, while related to navigation and precision approaches, serve different functions. The glideslope, for example, provides vertical guidance for the descent path but does not offer horizontal alignment. A VOR (VHF Omnidirectional Range) is also a navigational aid but does not specifically align with runways. The ILS as a whole includes the localizer and glideslope but does not specifically identify the horizontal guidance aspect. Thus, identifying the localizer as the instrument that transmits in VHF and offers horizontal guidance is accurate and aligns perfectly with its purpose in aviation navigation.