判断题 A phoneme is the smallest distinctive sound unit, incapable of change in different phonetic environments.（）

判断题 Consonants vary depending on where and how the air stream gets through, the place and movement of the tongue, and also whether the voice is used or not.（）

判断题 Vowels are formed mainly by the position of the tongue and, secondarily, by the shape of the lips and movement of the jaw.（）