Answer: The correct answer is- D) Sweat.
Non specific defense is a type of immune response ( also called innate immune response) that does not target any specific disease causing organism ( pathogen such as any specific bacteria or virus).
It is mainly provided by the surface of body ( such as skin that acts as an important barrier against external agents).
Sweat is an example of non specific chemical defense as it makes the surface of skin ( epithelium) acidic, thereby inhibiting the growth of pathogens ( such as bacteria) on it.
Thus, option D) is the right answer.