What port should be listening before a successful connection is possible?

CORRECT TEXT
An administrator is configuring a secured webserver, however connecting to https://127.0.0.1 is
not working. She runs netstat -ntl, which returns the following output:
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN
What port should be listening before a successful connection is possible? (Provide only the numerical value of the port)

A.

B.

C.

D.