Which process contributes to the cloudiness of water?

Turbidity is the correct answer because it refers to the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye. These particles can include sediment, organic matter, and other pollutants that can affect water clarity. In natural and artificial water bodies, turbidity can arise from various sources such as soil erosion, runoff from land, and the presence of microorganisms or pollutants.

In contrast, filtration is a process aimed at removing impurities from water rather than contributing to its cloudiness. Eutrophication refers to the excessive growth of algae in water bodies due to nutrient enrichment, which can subsequently lead to increased turbidity as decaying algae contribute to the cloudiness. Decomposition is the breakdown of organic matter, which can also increase turbidity, but it is a specific process rather than a direct measure or cause of cloudiness like turbidity itself. Thus, turbidity is the most direct term that describes the state of cloudiness in water.