The correct answer is B) the amount of cooling water to the condenser is insufficient. The back pressure trip on a ship's service turbo-generator is designed to protect the turbine from damage by tripping the turbine if the amount of cooling water to the condenser is insufficient. This can occur if the cooling water pump fails or the cooling water supply is disrupted, causing the temperature and pressure in the condenser to rise. The back pressure trip senses this high back pressure and automatically shuts down the turbine to prevent damage from the excessive heat and pressure. The other options are incorrect because they do not directly relate to the function of the back pressure trip. Excessive cooling water, low lubricating oil pressure, or high gland seal leak off pressure would not trigger the back pressure trip, which is specifically designed to respond to insufficient cooling water flow to the condenser.