Which of the following statements is true about olfaction?

A) It occurs when a molecule binds to the surface of an olfactory cilium.
B) It occurs when molecules responsible for odor are transported to the cerebrum by the axoplasmic flow.
C) It occurs when pressure is applied to the olfactory cilia.
D) It occurs when potassium and sodium channels are closed by a chemical stimulus.
E) It occurs when molecules enter specialized olfactory cells.