Concept:Olfaction is the detection of chemicals in the air after they dissolve in nasal mucus, leading to a nerve signal that reaches the brain.
Explanation:In mammals, odor molecules enter the nose as airborne chemicals.
These chemicals dissolve in the layer of mucus lining the nasal cavity.
The dissolved chemicals stimulate sensory cells in the olfactory epithelium.
These sensory cells generate nerve impulses.
The impulses travel along the olfactory nerve to the brain, where the smell is perceived.
Therefore, the correct order involves dissolved chemicals, sensory cells, the olfactory nerve, and finally the brain.
Answer:D. dissolved chemicals → sensory cells → olfactory nerve → brain