30.It is generally assumed that the cell membrane of a receptor cell has various sites that combine with different chemicals. ______ A preference for sugar, the so-called sweet tooth, is common among many animals, and taste cravings to compensate for dietary or hormonal imbalances are well known. (A) The sensations perceived in the brain evidently result from a complex coding of the electrical impulses transmitted by the receptor cells. (B) A single taste receptor cell may alter its output of electrical impulses to any three or four of these so-called modalities (C) The tympanic membrane of the inner ear is mysteriously related to our perception of taste. (D) Often, smell plays an important role in the perception of many sensations considered to be tastes. (E) Because of the accessibility of taste receptors in some insects, much of the fundamental research on taste mechanisms has been conducted on these animals.