1. Both Lucy and Lily have been to the Great Wall. (改为否定句)
    _____ Lucy _____ Lily has been to the Great Wall.
2. The book cost ten yuan. (对画线部分提问)
   _____ _____ _____ the book cost?
3. He was reading a novel when the teacher came in. (改为一般疑问句)
   _____ _____ reading a novel when the teacher came in?
4. Where does he live? I don't know. (改为含有宾语从句的句子)
    I don't know______ _____ _____.