Viết lại các câu sau sao cho nghĩa không thay đổi
1. She last wore that dress at her sister's wedding.
    She hasn't _________________________________.
2. Jack London didn't write the novel ''The Adventures of Tom sawyer''.
    The novel __________________________________.
3. Computers are used to design new models.
    People ____________________________________.
4. When did you start working in that factory?
    How long __________________________________.