You want to enable your users to use ssh to log in to your system, and to forward X11 connections from your server to their workstations. The server sits behind a firewall that refuses all incoming and outgoing connections. Which port(s) should you open on the firewall?

A.
22 only

B.
22 and 6000

C.
22 and 6010

D.
22 and 6010-6020