Explanation:

- Silt: Though primarily a natural sediment, when it accumulates excessively in water bodies, it can disrupt aquatic habitats and water quality.

- Glacier: Glaciers are large ice masses and not typically pollutants. They store fresh water and regulate sea levels. ?? Correct Answer

- Arsenic: A toxic element often found in water due to natural deposits or agricultural/industrial activities. It poses significant health risks.

- Chromium: A metal that can contaminate water, especially in its hexavalent form, from industrial waste and poses serious health dangers when ingested.