Final answer:
The olfactory nerve (CN I) is a purely sensory cranial nerve that transmits smell information from the nose to the brainstem.
Step-by-step explanation:
The type of cranial nerve that the olfactory nerve (CN I) is classified as purely sensory. This nerve is responsible for transmitting information about smells from the nose to the brainstem. The olfactory nerve consists of olfactory neurons which are specialized bipolar neurons; they possess receptors on their cilia that are sensitive to different odorants. When an odorant molecule binds to a matching receptor, it stimulates the sensory neuron, causing an action potential that transmits the information to the brain.