Mr. Green teaches English in a middle school. He has two children. They are twin sisters. Mr. Green calls them Lisa and Lily. Tim and Sue are Mr. Green's students. They are in the same class. They often go to see the twins and play with them. Sometimes they bring something to Lisa and Lily. One day they go to Mr. Green's house. When the twins see Tim and Sue, they are very happy. Tim asks Lisa, "How old are you, Lisa?" "Three, "Lisa answers. Sue behind Tim says, "Lisa and Lily, look! Oranges. Don't you want to eat? Well, l have a question. If you can answer well, you can eat. "The twins listen to Sue carefully. "l have two oranges, now l eat one. How many oranges do I have, then?"

"One, "Lisa says. Lily says, "Two. ""Two?" Tim says. "Why?"

"Oh, one is inside and the other is outside. "