Where did the conversation take place

A．"Microfilm" is a tiny square film no bigger than your thumbnail.
B．To borrow a microfilm you do not need to find out the call slip.
C．You can read the materials on a microfilm directly.
D．You must use a machine to read the material on a microfilm.

A．Current issues are kept on the shelves.
B．Back issues are bound together in volumes.
C．The procedure of borrowing a back issue is slightly different from that of a book.
D．Current issues of periodicals are put on microfilm.