The phrase '2.5' by 2.5'' in this context refers to the size of a what?

• A. Sector
• B. Contour interval
• C. Grid cell
• D. drainage area

Answer: (A)

Think of how the chart or diagram is laid out: it’s often divided into wedge-shaped pieces around a center, called sectors. When you see a two-dimensional size like 2.5 by 2.5, that’s indicating the footprint or bounding box that a single sector occupies on the plotting area. In this context, the description is about the size of a sector, not a square grid cell, not the vertical spacing between contour lines, and not a watershed. A grid cell would typically be described by equal lengths on both axes, while a contour interval is about elevation spacing, and a drainage area is a hydrologic feature rather than a plotted unit. So the 2.5 by 2.5 measurement refers to the size of a sector.