试题题干
Vocabulary is the most unstable element of a language as it is undergoing constant changes both in form and（）.
参考答案
正确答案：
试题解析
词的形式和内容总是处于变化之中，所以词是语言中最不稳定的因素。
Vocabulary is the most unstable element of a language as it is undergoing constant changes both in form and（）.
词的形式和内容总是处于变化之中，所以词是语言中最不稳定的因素。