The number of square units needed to cover a surface.

• A. Area
• B. Perimeter
• C. Radius
• D. Volume

Answer: (A)

Area is the measure of the two-dimensional space inside a boundary, and it’s expressed in square units because it describes flat surface coverage. When you’re figuring out how much material is needed to cover a surface, you’re asking for how much area that surface has, not how long its edge is or how much 3D space it contains. Perimeter measures the distance around the edge (a length), radius is a distance from the center to the edge, and volume describes the amount of space inside a solid (cubic units). For a rectangle, area equals length times width; for a circle, area equals pi times radius squared. So the number of square units needed to cover a surface corresponds to the area.