Your company has a single Active Directory domain. The company network is protected by a firewall. Remote users connect to your network through a VPN server by using PPTP.When the users try to connect to the VPN server, they receive the following error message:Error 721:The remote computer is not responding.You need to ensure that users can establish a VPN connection. What should you do?()
A.Open port 1423 on the firewall.
B.Open port 1723 on the firewall.
C.Open port 3389 on the firewall.
D.Open port 6000 on the firewall.