The correct answer is: C. Localizer and L.M.M. are installed on one side and L.O.M. on the other side.
The instrument landing system (ILS) is an instrument approach system that provides precision lateral and vertical guidance to an aircraft approaching and landing on a runway, using a combination of radio signals and, in many cases, high-intensity lighting arrays to enable a safe landing during instrument meteorological conditions (IMC), such as low ceilings or reduced visibility due to fog, rain, or blowing snow.
The ILS consists of two radio transmitters, the localizer and the glide slope. The localizer transmitter emits a signal that is used to guide the aircraft down the centerline of the runway. The glide slope transmitter emits a signal that is used to guide the aircraft to the correct altitude as it descends to the runway.
The localizer and glide slope transmitters are typically located on either side of the runway, with the localizer antenna located on the side of the runway that is closest to the approach end, and the glide slope antenna located on the side of the runway that is closest to the touchdown zone.
The L.O.M. (Localizer Outer Marker) is a marker beacon that is located approximately 750 feet from the approach end of the runway. The L.O.M. emits a signal that is used by the aircraft to verify that it is on the correct approach path.
The L.M.M. (Localizer Middle Marker) is a marker beacon that is located approximately 300 feet from the approach end of the runway. The L.M.M. emits a signal that is used by the aircraft to verify that it is on the correct glide path.
The ILS provides a safe and reliable way for aircraft to land in low visibility conditions. It is a critical piece of infrastructure for airports around the world.