填空题Below are some notices and signs from a trade exhibition.
Explain what each one means using may, should, shouldn't, must, mustn't, don't
have to. PLEASE USE OTHER DOOR You
shouldn't use this door. MEETING ROOM 6 Knock and
enter 1. ______ No Photography in Main
Hall 2. ______ AUTHORIZED PERSONNEL
ONLY 3. ______ Present badges HERE (except
staff) 4. ______ REGISTER HERE
5. ______ Events catalogue Please take
one 6. ______