Final answer:
Antivirus software and firewalls are tools used to protect XYZ's network from external threats.
Step-by-step explanation:
The correct answer is a) Antivirus software and firewalls.
Antivirus software is used to detect and remove malicious software (malware) that can harm a computer or network. It scans files, websites, and email attachments for known threats and takes action to protect the system.
Firewalls, on the other hand, are a network security tool that monitors and controls incoming and outgoing network traffic. They act as a barrier between an internal network and the external network (like the internet) to prevent unauthorized access and protect against potential threats.