Complete the following statements with proper words or expressions according to the course book.Vocabulary is the most unstable element of a language as it is undergoing constant changes both in form and ( ).
【正确答案】：CONTENT
【题目解析】：Vocabulary is the most unstable element of a language as it is undergoing constant changes both in form and content. 词汇是语言中最不稳定的一种要素，因为它在形式和内容上都在不断变化。
