[解析]
1.not a bad thing 细节理解题.根据"Language is always changing and developing.This isn't a bad thing."可知作者认为语言的发展变化不是坏事情,故答案为not a bad thing.
2.ages,jobs 细节理解题.根据"People use different sets of words and expressions,because they have different ages,jobs,education levels and so on."可知人们用不同的单词和短语,因为他们有不同的年龄、工作和受教育水平等.故答案为ages,jobs.
3.two.细节理解题.根据"First,it changes because the needs of its speaker change."和"Another reason for change is that different people have different language experiences."可知本文提到了语言变化的两个原因,故答案为two.
4.communicate with 细节理解题.根据"When young people communicate with others of their own age,their language grows in grammar,words and expressions that are different from the older people's."可知年轻人和同龄人交流时,他们的语言在语法、词汇和短语不同于年长的人.故此处为communicate with.
5.doesn't change 细节理解题.根据"Languages that don't change over time are considered dead languages."可知不随着时间而变化的语言被认为是死语言.先行词The one为三单,故从句中的谓语动词用does,故答案为doesn't change.