单项选择题 The fact that different languages have different words for the same object is good proof that human language is （）.

单项选择题 In terms of the place of articulation, the following sounds [t][d][s][z][n] share the feature of （）.

单项选择题 What the element ‘-es’ indicates is third person singular, present tense, the element ‘-ed’ past tense, and ‘-ing’ progressive aspect. Since they are the smallest unit of language and meaningful, they are also（）.