单选题 .  Under normal conditions the act of communication requires the presence of at least two persons: one who sends and the other who receives the communication. In order to communicate thoughts and feelings, there must be a conventional system of signs and symbols which means the same to the sender and the receiver.
    The means of sending communications are too numerous and varied for systematic classification; therefore, the analysis must begin with the means of receiving communication. Reception of communication is achieved by our senses, of which sight, hearing and touch play the most important roles.
    Examples of visual communication are gesture and mimicry. Although both frequently accompany speech, there are systems that rely solely on sight, such as those used by deaf and dumb persons. Another means of communicating visually is by signals of fire, smoke, flags, or flashing lights. Feelings may be simply communicated by touch, such as by hand-stroking. Although a highly developed system of hand-stroking has enabled blind, deaf and dumb persons to communicate intelligently. Whistling to someone, applauding in a theatre, and other forms of communication by sound rely upon the ear as a receiver. The most fully developed form of auditory communication is, of course, the spoken language.
    The means of communication mentioned so far have two features in communication: they last only a short time, and the persons involved must be relatively close to each other. Therefore, all are restricted in time and space.1.  In the author's opinion, the reception of communication should be dealt with first because ______.