Little Tom down the street calls our dog "the keep dog". Zip is a sheep dog. But when Tom tries to say "sheep", it comes out "keep". And in a way Tom is right. Zip is always bringing things home for us to keep! I’ll tell you about some of them. Zip’s first present was a shoe. It was made of green silk. We didn’t know how Zip found the shoe. But after a moment Mary, my big sister, told me the shoe had a strange smell. I nodded(点头) and held my nose. "What do you think it is" "It smells like something for cleaning. I think someone tried to clean a spot(污点) off the shoe. Then he put it at the door to dry." "Along came Zip. And good-bye shoe!" I said. "We should take it back." "We can’t," said my sister. "We don’t know where Zip found it." "Maybe little Tom is right," Mary said. "Maybe Zip is a keep dog!\ What made them fail to take the shoe back