A reflex action is a quick involuntary response to stimulus. Which of the following is an example of both, unconditioned and conditioned reflex?

The correct option is C Secretion of saliva in response to the aroma of food
An unconditioned reflex is a reflex that is either inborn or has physiological maturation dependence. It is no based on learning. A conditioned reflex is the one which is based on learning. Saliva secretion is controlled by both unconditioned and conditioned reflexes.

Pavlov's experiment is used to understand this in detail.

On seeing food by the dog, the taste buds on its tongue stimulate receptors present in the brain that in turn stimulate the salivary glands to secrete saliva Hence it is an unconditioned reflex.

The food was served to the dog after ringing the bell every time. Hence the dog associated the sound of the bell with food and would salivate even when food is not served and only bell is rung. The dog developed this reflex action by learning. Hence it is also a conditioned reflex.

Thus the correct answer is option B.