A valley can be described as which of the following?

A valley is best described as a low area surrounded by higher ground, which aligns with the definition that highlights its geographical context. It typically forms between hills or mountains due to the processes of erosion and weathering.

In geographical terms, valleys are often characterized by their lower elevation compared to the surrounding terrain, which can consist of elevations such as hills or mountains on either side. This definition emphasizes the defining feature of a valley as a depression, contrasting with the surrounding high areas.

The other descriptions do not accurately capture the essence of a valley. For example, a flat area between two high points does not convey the specific depression aspect; instead, it could refer to plains or plateaus. Describing a valley as a long and narrow depression in the landscape might seem similar, but it doesn’t account for the broader context of being surrounded by higher ground. Lastly, an elevated area with steep sides directly contradicts the low elevation characteristic integral to a valley's definition. Understanding these concepts is crucial for anyone studying terrain and landforms in a military context, as it influences strategic decisions based on geographic advantages or disadvantages.