The correct answer is B) start the cargo pump, then open sea suction valves. The reasoning behind this is that to prevent oil from escaping into the sea during ballasting, you should first start the cargo pump to create a flow through the cargo piping system. This ensures that the system is pressurized and any oil in the piping will be drawn into the cargo tanks rather than escaping into the sea. Once the pump is running, you can then open the sea suction valves to allow the ballast water to be taken in without risk of oil spilling. The other options are incorrect because they do not properly sequence the steps to prevent oil from escaping. Opening sluice valves or block valves without first starting the pump could allow oil to be drawn out, and opening sea suction valves before starting the pump would not create the necessary flow to contain the oil.