Which of the following systems describes an abbreviated precision approach path indicator:
Twenty light units symmetrically disposed about the runway centre line in the form of two wing bars of four light units each, with bisecting longitudinal lines of six lights
A wing bar of 4 sharp transition multi-lamp units equally spaced and normally located on the left side of the runway unless it is physically impracticable to do so
Ten light units arranged on one side of the runway in the form of a single wing bar of four light units, with a bisecting longitudinal line of six lights
A wing bar of 2 sharp transition multi-lamp units normally located on the left side of the runway unless it is physically impracticable to do so