Which landform is created at the mouth of the river, formed by deposits of silt and dis-tributaries?

The correct choice is a delta, which is a landform that occurs at the mouth of a river where it meets a body of water, such as an ocean, sea, or lake. As the river flows towards its mouth, it carries sediment, which consists of silt, sand, and clay. When the river slows down upon entering a larger body of water, it loses the energy required to carry these sediments, leading to the deposition of materials at its mouth.

The accumulating sediments over time create a delta, characterized by a network of distributaries, which are smaller channels that branch off from the main river. Deltas are often fertile and support diverse ecosystems due to the nutrient-rich sediments deposited there, making them important for both ecological and human activities such as agriculture.

While estuaries are also found where rivers meet bigger bodies of water and involve mixing of fresh and saltwater, they do not primarily result from sediment deposition forming a distinct landform like deltas do. Dunes, on the other hand, are formed by wind-blown sand, typically in arid or coastal regions, and ox-bow lakes are remnants of river meanders that have been cut off, rather than being formed by sediment deposition at the mouth of a river.