An electrode is inserted into a chemosensory nerve fiber leading away from a taste bud in the mouth of a dog. A mild acid solution is then flushed continuously over the taste buds associated with this nerve. Initially the nerve responds to this stimulation, but over time ceases to carry action potentials. This observation would best be explained by which of the following?

A. Adaptation of the sensory cells.

B. Lack of neurotransmitter in the sensory nerve.

C. Second messenger influences that increase cell membrane potentials.

D. Translocation.