18. Look at the picture. If you see this sign, which statement is not true? HK Library Sorry! We are closed. To return a book, please use a drop box or call our staff at 456 - 7392 a. You cannot return a book because the library is closed. b. You can contact staff to return a book. c. You cannot enter the library today. d. The library will open tomorrow.

If the sign indicates that the library is closed, it suggests that option "a" is not true. While the library is closed, you can still return a book using the drop box. So, it's not correct to say you cannot return a book! Additionally, the statement "c" implies you cannot enter the library today, which could also be seen as inaccurate depending on if there was an emergency or special access allowed. Libraries sometimes offer alternative entry points for emergencies!