Complete the following statements with proper words or expressions according to the course book.The world has about 3000（some put it 5000） languages, which can be grouped into roughly 300 language families on the basis of similarities in their basic word stock and ( ).
【正确答案】：GRAMMAR
【题目解析】：据估计, 世界上约有 3000多种(有人认为有5000种)语言。这些语言可以根据他们的基本词汇和语法的相似性大致划为300个谱系。
