Final answer:
An operating system is not application software; it is the foundational software that manages hardware resources. In contrast, Word Processors, Spreadsheets, and Web Browsers are all types of application software designed for specific tasks.
Step-by-step explanation:
The question is asking to identify which option among the given is not categorized as application software. Application software is designed to carry out specific tasks for the user, such as word processing, spreadsheet calculation, or web browsing.
Operating system software, such as Microsoft Windows, is responsible for managing hardware resources and providing common services for computer programs. Therefore, an operating system is not an application software but rather the foundational software that allows application software to run.
On the other hand, a Word Processor such as Corel WordPerfect, Spreadsheet software like Microsoft Excel, and a Web Browser are all examples of application software as they are designed for end-users to perform specific, productivity-related tasks.