A lighthouse description on a SHOA chart reads: 'Gp Oc(3) W 15s 24m 18M'. How should this light characteristic be interpreted by the skipper?

1. Group Occulting showing 3 eclipses/dark periods, White light, period of 15 seconds, focal height 24 meters, nominal range 18 nautical miles
2. Group Flashing showing 3 flashes, White light, period of 15 seconds, elevation 24 meters, nominal range 18 nautical miles
3. Quick Flashing 3 times, Green light, 15 minutes duration, 24 miles visibility, 18 meters height
4. Fixed light with 3 sectors, White light, 15 seconds period, 24 meters beam width, 18 nautical miles range