Final answer:
Olfactory cells are a type of neuron that contain receptors for odor molecules and are part of the sensory system, distinguishing them from other nasal cavity cells. Option c.
Step-by-step explanation:
Olfactory cells, which are responsible for the sense of smell, are a type of neuron. These cells contain receptors for odor molecules and are part of the sensory system. They are not directly related to the respiratory cells or mucus cells, which have different functions like trapping debris and warming and humidifying incoming air. Although olfactory cells are located in the nasal cavity, and the nasal cavity does include respiratory epithelium, olfactory cells themselves fall under the category of neurons due to their role in transmitting information to the brain.