Final answer:
A. Filtering software is responsible for preventing a browser from showing content from specific sites or those containing certain keywords.
Step-by-step explanation:
Filtering software prevents your browser from displaying materials from targeted sites or sites that contain certain keywords or phrases. Filtering software can be implemented as a standalone application, as part of a firewall, or as a feature within browser extensions. It is designed to block content that is deemed inappropriate or unsafe, especially useful in educational or family-friendly environments. It differs from antivirus software, firewalls, and browser extensions, although it can sometimes be part of these tools.
Antivirus software is aimed at protecting a computer from malware and viruses, rather than blocking content based on site or keyword criteria. A firewall restricts unauthorized access to or from a private network, while browser extensions can provide a variety of features and enhancements to web browsing, including ad-blocking and privacy-focused functions.