Final answer:
Extensions option b is correct, are the add-ons that enhance browser functionality in new and unintended ways, offering a wide range of additional features.
Step-by-step explanation:
The type of add-on that will extend the functionality of a web browser in a way it wasn't originally designed is B. Extensions. Extensions are software modules that developers create to add new features or extend the capabilities of a browser.
These can range from tools for productivity, such as note-taking apps, to entertainment functionalities like games. While pop-up blockers and ad blockers mainly focus on inhibiting content, and plug-ins typically enable support for specific types of content like video playback, extensions can completely change how browsers operate and interact with web content and services.
They can add new functionality, such as blocking ads, improving security, or providing additional tools for productivity.