Stress is the force exerted per unit area on an object. The term mental stress refers to the psychological strain or pressure experienced by an individual. It is the pressure resulting from various internal or external factors, such as workload, emotions, or anxiety.
The correct type of strain corresponding to stress in a psychological context is mental strain.
Stress, in a physical context, refers to mechanical stress, but when we focus on psychological aspects, it refers to mental stress. Therefore, the correct answer is Mental strain.