What does "hummock" refer to in the context of geography?

In geography, a "hummock" refers to a small, elevated area of land, commonly known as a knoll. This term is often used to describe a naturally occurring hill or mound that is smaller than a mountain and may be formed through various geological processes, such as erosion or the accumulation of sediment. Hummocks can be found in diverse landscapes, including marshes and tundras, and they can play a significant role in local ecosystems by providing different habitats for plant and animal species. The definition aligns precisely with the characteristics of a knoll, reinforcing the correct choice.

In contrast, the other options do not accurately reflect the meaning of "hummock." A swing refers to a hanging seat, a valley represents a low area between hills or mountains, and a backyard designates an outdoor space adjacent to a home, none of which relate to the geographical context of a small hill or mound.