The correct answer is B) A long swell from an unusual direction. A long swell from an unusual direction can indicate the formation of a tropical storm or hurricane several hundred miles away. This is because distant low-pressure systems, like those associated with developing tropical cyclones, can generate long ocean swells that propagate outward from the storm center. These swells typically arrive before other signs of the approaching system, providing an early indication of its presence and location. The other options are incorrect because: A) Large seas from different directions are more likely caused by local wind shifts or the interaction of multiple wave systems, not a distant storm. C) A lull in wind and seas is more indicative of a high-pressure system, not an approaching low-pressure cyclone. D) A chop from the southeast would not necessarily indicate a distant tropical system, as it could be caused by various local wind patterns.