One day a bookseller （书商） let a big box of books fall onhis foot."Go to see the doctor," said his wife."No," hesaid." 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 thebookseller was getting them ready, he told the doctor about his bad foot.Thedoctor looked at it.
"You must put that foot in hot water every night.Then you must putsomething on it," said the doctor.
He took out a piece of paper and wrote on it."Buy this and put it on thefoot before you go to bed every night," he said.
"Thank you," said the bookseller."And now, sir, here are yourbooks."
"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 tomy house, I ask them to pay one pound for a small thing like that.But when I goto their houses, I
want two pounds.And I came here, didn't I?"

The doctor paid________ for the books.

A.one pound

B.two pounds

C.nothing

D.something