The correct answer is B. Eutrophication.
Eutrophication is the process by which a water body becomes enriched with nutrients, particularly phosphorus and nitrogen. This can lead to excessive growth of algae and other aquatic plants, which can then die and decompose, depleting the water of oxygen and suffocating fish and other aquatic life.
Smog is a type of air pollution that is caused by the combination of smoke and fog. It is most common in urban areas, where it can cause respiratory problems and other health issues.
The greenhouse effect is a natural process that warms the Earth’s surface. It is caused by the presence of greenhouse gases in the atmosphere, which trap heat from the sun.
None of these options are correct.