The following excerpt is from what standard network configuration file?

ftp        21/tcp
fsp        21/udp        fspd
ssh        22/tcp                    # SSH Remote Login Protocol
ssh        22/udp
telnet     23/tcp
smtp       25/tcp        mail
time       37/tcp        timserver
time       37/udp        timserver
rlp        39/udp        resource    # resource location
nameserver 42/tcp        name        # IEN 116
whois      43/tcp        nicname

A.
/etc/hosts

B.
/etc/inetd.conf

C.
/etc/services

D.
/etc/syslog.conf

Explanation:
From the man pages:
services is a plain ASCII file providing a mapping between human-friendly textual names for internet services, and their underlying assigned port numbers and protocol types.