After an upgrade of network equipment and applications, users are no longer able to access the Internet. Internal resources, such as file servers and databases, are accessible to the users. Which of the following is the MOST likely cause?
A. The firewall is blocking outbound port 80 traffic.
B. The web server was placed in the network’s DMZ.
C. The NetBIOS ports were left open on the firewall.
D. The user PCs and the web server are both using IPv6.