What is a "knoll"?

A "knoll" refers to a small natural hill, which is typically characterized by its rounded shape. This term is often used in geography to describe elevated landforms that are smaller than mountains or large hills. Knolls can vary in size but are generally low enough to not be considered significant elevations in a landscape. The context of the word often relates to scenery and natural topography, making it a common term in discussions about geography, ecology, or outdoor environments.

The other options do not align with the definition of a knoll. Animals, ocean waves, and valleys refer to entirely different categories and features in nature, highlighting that a knoll specifically denotes a hill rather than anything else listed.