11: 阅读理解单选题One day a bookseller (书商) let a big box of books fall on his foot. “Go to see the doctor,” said his wife. “No,” he said, “I’ll wait until the doctor comes into the shop next time. Then I’ll ask him about my foot. If I go to see him, I’ll have to pay him.”On the next day the doctor came into the shop for some books. When the bookseller was getting them ready, he told the doctor about his bad foot. The doctor looked at it.“You must put that foot in hot water every night. Then you must put something on it,” said the doctor.He took out a piece of paper and wrote on it. “Buy this and put it on the foot before you go to bed every night,” he said.“Thank you,” said the bookseller. “And now, sir, here are your books.”“How much?” said the doctor.“Two pounds.”“Good,” said the doctor. “I shall not have to pay you anything.”“Why?” asked the bookseller.“I told you about your foot. I want two pounds for that. If people come to my house, I ask them to pay one pound for a small thing like that. But when I go to their houses, I want two pounds. And I came here, didn’t I?”