An environmental agency is assessing the ecological impact of various petroleum-derived fuels in the event of an aquatic spill. The persistence of a spill on the water surface is largely determined by the volatility and viscosity of the hydrocarbon fraction, which are directly governed by the strength of its intermolecular forces.

Four fractions are compared: petrol, kerosene, diesel oil, and fuel oil. Which of these fractions will resist evaporation the most and leave the most viscous, persistent residue due to having the strongest intermolecular forces?