Which of the following best defines stress in the context of mechanical properties of solids?
Stress is defined as the restoring force per unit area developed in a body due to an external deforming force, given by Stress = FA. As per NCERT, applying relevant law/formula with correct units and sign convention leads to Restoring force per unit area. This satisfies dimensional consistency and physical conditions given, so option A is scientifically correct.
Ref: NCERT Class 11 Physics, Thermal Properties and Gravitation.