题目内容：
阅读下短文，回答题：根据中文提示，将对话中缺少的内容写在线上。这些句子必须符合英语表达习惯。打句号的地方，用陈述句；打问号的地方，用疑问句。
提示：Charles一周前开始背疼，他今天早上去看医生。医生检查后告诉他卧床休息两天，就会感觉好一些。他问大夫是否吃点药，医生给他一些药，告诉他一天吃三次，每次吃一片。
( Doctor = D; Charles = C)
D: __________51__________. Come in and sit down.
C : Hello, doctor.
D: __________52__________?
C : I've got a backache.
D:Do you often have a backache？
C:No,I don't. I've never had a bad one before.
D:When did it start?
C:__________53__________.
(The doctor examines Charles carefully. )
D: Well, go home and：__________54__________, then you'll feel better.
C:Can you give me some medicine? It's very painful.
D : Yes, I'll give you some .pills.__________55__________, and come
back in two days if you don't feel any better.
请回答第51空：
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