单选题 Duality means that language has the property of having two levels of structures, such that units of the primary level consists of elements of the secondary level and each of the two levels has its own principles of organization.
【正确答案】 A
【答案解析】解析：考查语言的二重性。二重性指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，每层都有自身的组合规则。底层结构由一些本身没有意义的语音组成，但是它们可以各自组合成有意义的单位，从而形成具有独特、确定意义的上层单位。上层单位能够被组合或重新组合成特定数量的句子。