Concept:The Post Office Protocol (POP) is an application-layer protocol used for retrieving email from a mail server.
Explanation:POP allows an email client to connect to a remote mail server.
The client downloads the stored email messages to the user's local device.
After retrieval, emails may be removed from the server, letting users read them offline.
POP is not designed for sending email or transferring files.
It also does not interconnect devices on the Internet.
Its main purpose is simply to fetch email from a mail server to a client.
Answer:The correct option is B. retrieve email from a mail server.