Which sequence correctly explains the formation of an oxbow lake in the Northern Plains?

Correct answer: A meander neck is cut off and a separate lake forms

An oxbow lake forms when a river meander becomes isolated from the main channel. A meander is a wide bend in a river. Erosion acts more strongly on the outer banks, while deposition occurs on inner banks, gradually narrowing the neck of the bend. During a flood or continued erosion, the neck may be cut through. The river then follows a shorter course, leaving the old curved loop as a separate lake.

Option D is correct because it describes this cut-off process. The new lake often has a curved or horseshoe-like shape and represents an abandoned part of the former river channel. The other options involve mountains, lava, glaciers, or deltas and do not explain oxbow formation. The essential sequence is meander development, neck cut-off, and separation from the active river.