【正确答案】正确答案：Duality refers to the property of having two levels of structures, such that units of the primary level are composed of elements of the secondary level and each of the two levels has its own principles of organization.(2 points)To talk about duality we must notice that language is hierarchical. As Bolinger and Sears put it, " Stratification—this organization of levels on levels—is the physical manifestation of the " infinite use of finite means" , the trait that most distinguishes human communication and that provides its tremendous resourcefulness. "(2 points)The advantage of duality lies in the great productive power our language is endowed with.(1 point)

【答案解析】解析：考查语言的二重性特征。二重性指语言拥有两层结构的这种特性，底层结构是上层结构的组成成分，每层结构都有自身的组合规则。在语言的二重性中，我们必须注意语言的等级性。鲍林格和希尔斯指出，分层——一级一级的组织——是有限的手段无限使用的物质表现，这是人类语言最显著的特征，并为之提供巨大的潜能。现在我们能够理解二重性的优势，它使语言拥有了一种强大的能产性。