What best describes a depression in topographic maps?

Answer: A — contour line that forms concentric circles or ovals

A depression in topographic maps is accurately described as a contour line that forms concentric circles or ovals. This specific characteristic indicates a low area where the elevation decreases as you move toward the center of the depression. The inner contour lines represent successively lower elevations, visually depicting the topographic feature. When interpreting topographic maps, understanding how depressions are represented is crucial for assessing land features. The concentric nature of the contour lines distinctly differentiates depressions from other landforms, such as hills or ridges, where the contour lines would typically indicate rising elevation. The other choices do not appropriately describe depressions. The notion of land surface irregularities may apply broadly but does not specifically convey what a depression is. The concept of a straight line representing equal distances pertains more to scale rather than topography, and a line indicating sea level relates to a specific elevation reference rather than defining a depression itself.