单项选择题
A.communication by sound B.gesture and mini-cry C.communication by touch D.a simple system of visual communication
A.communication actually takes place when the message is received B.there are more means of receiving than sending communications C.reception of communications involved use of the senses D.it is difficult to organize by type the means of sending communications
A.consult students about the books required for their studies B.provide work for students in the library C.provide books for students to consult D.test students' ability to use the resources in libraries