Which of the following should you install if you want to control which ports of the

server are open to the Internet?

A.
A firewall.

B.
Antivirus programs.

C.
Virus software updates.

D.
All of the above.

Explanation:
If you want to control which server ports are open to the Internet, you should install a firewall solution. Firewall solutions are available as hardware and software components.
A firewall can also detect when any intrusion attempts are made by hackers.
Incorrect Answers:
B: Antivirus programs provide protection against viruses that can infect and cause damage to your server systems. Antivirus programs do not allow you to define which ports are open/close to the Internet.
C: Virus software updates are released by software manufacturers to protect your server systems from new viruses.
D: A firewall is the correct answer.
References:
Charles J. Brooks, Server+ Certification Exam Cram 2 (Exam SK0-002), QUE Publishing, Indianapolis, 2006, pp. 458-459.