The correct answer is option 2, Oxbow lake. An oxbow lake is a curved body of water formed from a meandering river. It is created when a river undergoes erosion and deposition processes.

First, the river erodes the outer bend of a meander, forming a neck that narrows over time. As the erosion continues, the neck becomes smaller, until eventually, the river breaks through the narrowest part of the meander neck during a flood event. This process is known as a cutoff.

Once the cutoff occurs, the river takes the path of least resistance, flowing straighter and leaving behind a curved lake or lagoon. This lake is known as an oxbow lake. The deposition of sediment along the newly formed cutoff contributes to the formation of the oxbow lake.

Oxbow lakes are often found in floodplain areas and exhibit a characteristic U-shape. They are a common feature of mature river systems and can provide habitats for various plant and animal species.