What service is being accessed?

Your server logfile shows repeated connections to TCP port 143. What service is being accessed?

A.
smtp

B.
imap

C.
pop3

D.
pop2

E.
nmbd

Explanation:
From /etc/services:
imap2 143/tcp imap # Interim Mail Access P 2 and 4
imap2 143/udp imap