Which setting in the Courier IMAP configuration file will tell the IMAP daemon to only listen on the localhost interface?

Which setting in the Courier IMAP configuration file will tell the IMAP daemon to only listen on the localhost interface?

A.
ADDRESS=127.0.0.1

B.
Listen 127.0.0.1

C.
INTERFACE=127.0.0.1

D.
LOCALHOST_ONLY=1