Which configuration setting should the administrator verify to diagnose this problem?

A View Security Server has been configured to allow external RDP access using SSL to the internal View Desktops. Users are reporting that they are unable to connect.

Which configuration setting should the administrator verify to diagnose this problem?

A.
RDP access is enabled on the Security Server.

B.
The remote connection timeout is set to 10.

C.
Port 443 is open on the firewall.

D.
Port 3389 is disabled on the firewall.