Stress may be defined as A. Force per unit length B. Force per unit volume C. Force per unit area D. None of these

The correct answer is C. Force per unit area.

Stress is a measure of the internal forces acting on a material per unit area. It is a tensor quantity, meaning that it has both magnitude and direction. Stress can be caused by a variety of factors, including applied loads, temperature changes, and chemical reactions.

The SI unit of stress is the pascal (Pa), which is equal to one newton per square meter (N/m2).

Option A is incorrect because force per unit length is called linear stress.

Option B is incorrect because force per unit volume is called volumetric stress.

Option D is incorrect because stress is a real quantity that can be measured.