The correct answer is B) magnetic influence inherent to that particular vessel. Deviation is caused by the magnetic influence of the materials and equipment on the vessel itself. The compass on a ship is affected by the magnetic fields generated by the ship's structure, equipment, and cargo, causing the compass to deviate from true north. This deviation is unique to each vessel and must be accounted for through regular compass adjustment and compensation. The other options, while related to magnetism, do not directly cause the deviation experienced on a particular vessel.