The term "Diathesis" in diathesis stress model means:

Biological predisposition to the disorder

The correct answer is Option (1) → Biological predisposition to the disorder

In the diathesis-stress model, the term diathesis refers to an individual's biological or genetic vulnerability or predisposition to developing a psychological disorder. This predisposition, when combined with environmental stressors, may lead to the manifestation of a disorder. Thus, the model explains mental illness as a result of the interaction between a predispositional vulnerability and external stressful events.