【正确答案】正确答案：Sociolinguistics is an umbrella term which covers a variety of different interests in language and society, including the social functions of language and the social characteristics of its users. It studies the characteristics of language varieties, the characteristics of their functions, and the characteristics of their speakers as these three constantly interact and change within a speech community.

【答案解析】解析：（本题考查社会语言学的定义。)