ANS:C - unity of force/area.

"Unity of force/area" refers to the units of force divided by area. In the International System of Units (SI), the unit of force is the newton (N), and the unit of area is the square meter (m^2). Therefore, the unit of force/area is newton per square meter (N/m^2), which is equivalent to the pascal (Pa). The pascal (Pa) is the SI unit of pressure and is defined as one newton per square meter. It is named after the French mathematician, physicist, and philosopher Blaise Pascal. Pressure is defined as the force applied per unit area perpendicular to the direction of the force. It quantifies the amount of force distributed over a given area and is commonly used to describe the intensity of external forces acting on a surface. For example, atmospheric pressure is typically expressed in pascals, where 1 standard atmosphere (atm) is approximately equal to 101,325 pascals. In engineering and materials science, pressure plays a crucial role in various applications, including fluid dynamics, structural analysis, and material testing. The concept of force/area, or pressure, is fundamental to understanding how materials respond to external loads and how mechanical systems operate under different conditions.