Oil spreads on the surface of water primarily due to differences in surface tension between the two substances. The surface tension of water is higher than that of oil. This means that water molecules tend to stick together more strongly at the surface, forming a “skin” that resists penetration. In contrast, oil molecules have weaker intermolecular forces at the surface, allowing them to spread out more easily. This phenomenon occurs despite the fact that oil is less dense than water; option [D]. Oil molecules move to the water’s surface to minimize contact with water molecules, creating a thin layer. This behavior is essential in environmental contexts, such as oil spills, where oil can spread rapidly over large areas of water. Understanding the surface tension properties of oil and water is crucial for managing and mitigating the environmental impacts of such incidents.