The correct answer is B) after you start the fuel oil service pump. When warming up a fuel oil service system, it is important to start the fuel oil service pump first before opening the steam supply to the fuel oil heaters. This is because the pump needs to be circulating the fuel oil through the system in order for the heaters to effectively warm up the oil. If you open the steam supply before starting the pump, the heaters will not be able to heat the stagnant oil in the system. Starting the pump first ensures that the oil is flowing through the heaters, allowing them to efficiently raise the temperature of the fuel oil to the desired operating temperature. The other answer choices are incorrect because: A) opening the steam supply before the pump could lead to ineffective heating, C) the settlers should not be relied upon to heat the oil, and D) the recirculating valve should be opened after the pump is running and the heaters are warming the oil.