An oil spill is the accidental release of liquid petroleum into a water body — typically from tankers running aground, ruptured pipelines, or blowouts at offshore drilling platforms. By definition, the pollutants involved are petroleum products: crude oil and its refined fractions such as diesel, gasoline (petrol), and other hydrocarbons. This is why the petroleum-products option is correct.

Because these hydrocarbons are lighter than and immiscible with water, they spread into a floating slick with severe ecological consequences:

• The oily film blocks sunlight and interferes with gas exchange, lowering dissolved oxygen and harming plankton and photosynthesis.
• It coats the feathers of seabirds and the fur of marine mammals, destroying their insulation and buoyancy and causing them to suffocate or drown.
• It poisons and smothers fish, coral reefs, and shoreline organisms.
• Petroleum residues are persistent and can linger in sediments and coastlines for years.

The other options are genuine pollutants but are not the ones characteristic of ocean oil spills:

• Agricultural pesticides and chemical fertilizers are chiefly runoff pollutants of soil, rivers, lakes, and groundwater; fertilizer runoff in particular drives nutrient loading and eutrophication rather than an oil slick.
• Synthetic detergents are associated with water froth and eutrophication (their phosphates promote algal blooms), and are sometimes even used to disperse spilled oil — but they are not themselves the pollutant released in an oil spill.

Only petroleum products specifically define the pollutant group of an oceanic oil spill.