Which feature is formed inside a corrie?

A tarn is a small mountain lake found in a corrie, which is a bowl-shaped depression formed by glacial erosion. When a glacier moves and carves out this feature, it often leaves behind a hollow. After the glacier retreats, the resulting depression can fill with water, creating a tarn. This process is typical in glaciated landscapes, particularly in upland areas where conditions allow water to accumulate in the corrie's basin.

Other features mentioned, such as glaciers, do not form inside a corrie in the same way; instead, they are often responsible for creating the corrie itself through erosion. A tor refers to a rocky outcrop typically found on hilltops and is unrelated to the formation of features within a corrie. Lastly, while hills can be found surrounding corries, they are not formed within them, making a tarn the only accurate feature in this context.