填空题 Language is a system of a（）vocal symbols used for human communication.

填空题 D（）is one of the design features of human language which refers to the phenomenon that language consists of two levels: a lower level of meaningless individual sounds and a higher level of meaningful units.

填空题 Langue refers to the a（）linguistic system shared by all the members of a speech community while the parole is the concrete use of the conventions and application of the rules.