What is an outwash plain?

An outwash plain is specifically formed by the deposition of materials, such as sand and gravel, that are transported by meltwater flowing from a glacier. As the glacier retreats, it loses ice and releases large volumes of water, which carry sediment away from the glacial front. This sediment is then deposited, creating a flat, extended plain. The characteristics of an outwash plain include a stratified texture due to sorting of materials based on size by the flowing water, and these plains often have channels and other features related to water movement.

This makes "a plain formed by fluvoglacial deposition at the end of a glacier" the correct answer, as it encapsulates the process of sediment transport and deposition associated with glacial meltwater.