求新概念英语第2册第48课的背景

题目

求新概念英语第2册第48课的背景
附原文：
Lesson 48
Did you want to tell me something?
你想对我说什么吗?
First listen and then answer the question.
听录音,然后回答以下问题.
Why did the writer become very worried?
Dentists always ask questions when it is impossible for you to answer.My dentist had just pulled out one of my teeth and had told me to rest for a while.I tried to say something,but my mouth was full of cotton wool.He knew I collected match boxes and asked me whether my collection was growing.He then asked me how my brother was and whether I liked my new job in London.In answer to these questions I either nodded or made strange noises.Meanwhile,my tongue was busy searching out the hole where the tooth had been.I suddenly felt very worried,but could not say anything.When the dentist at last removed the cotton wool from my mouth,I was able to tell him that he had pulled out the wrong tooth.
New words and expressions 生词和短语
pull v.拔
cotton wool 药棉
collect v.搜集
collect

答案

什么背景?土豆网上有相关讲解动画,挺好的,去看看!