Mathematics ACT Aspire Practice Test 2025 - Free Practice Questions and Study Guide

The usual unit of measurement for surface area is square units because surface area refers to the total area that the surface of an object occupies. When measuring surface area, you're essentially calculating two-dimensional space, which is always represented using squared units. For instance, if you have a square with a side length of 2 units, the surface area would be calculated as side length multiplied by itself (2 x 2 = 4), giving you 4 square units.

Cubic units are used for volume measurements, where a three-dimensional space is involved, such as a cube. Linear units are used to measure length or distance in one dimension. The option "None of the above" does not apply since square units accurately describe the measurement used for surface area. Thus, square units is the correct choice for measuring surface area.