Answer:
Option (1)
Step-by-step explanation:
When a river enters a larger water body then it is called the mouth of the river. As the river enters the larger body of water, the inclination of the river decreases to nearly horizontal, as a result of which the flow velocity of the river decreases. Due to this, the river cannot further carry the sediments and deposits the materials such as sand, silt size particles, and clay. These accumulated materials are commonly known as alluvium. This area is known as the delta which is somewhat triangular in shape.
Thus, when a river enters a bigger water body, then it slows down and a large amount of sediment deposition takes place.
Hence, the correct answer is option (1).