What is true regarding TCP port 23?

A.
Port 23 is the well known port for the telnet service which is a plain text protocol that should no longer be used.

B.
Port 23 is the well known port for the SSH service which provides secure logins.

C.
Port 23 is the well known port for the rlogin service which is SSL secured by default.

D.
Port 23 is the well known port for the system login services which are encrypted when the user runs the starttls

command in his login shell.