Answer:
Taste and smell.
Explanation:
Receptor cells are able to respond against a particular stimuli. Main types of receptors are olfactory receptors, gustatory receptors, photo receptors, Tactile receptors and mechano receptors.
Gustatory receptors are present in the tastebuds and able to respond against the sense of taste. Olfactory receptors are able to respond against specific chemicals present in the environment and enable the sense of smell. Hence, gustatory and olfactory refers to the sense of taste and smell.
Thus, the correct answer is option 4.
