Final answer:
The Operating System is the crucial component to ensure the familiar look and feel of a computer's Graphical User Interface.
Therefore, the correct answer is: option F) Operating System
Step-by-step explanation:
An operating system is system software that manages computer hardware and software resources, and provides common services for computer programs.
The component most important to include to ensure the familiar look and feel of the Graphical User Interface (GUI) when purchasing a new computer would be the Operating System (F).
The operating system is the software that provides the foundation for all graphical elements, interfaces, and interactions that a user experiences.
While elements like the monitor (A) and video card (B) can impact the display quality and performance of graphics, the operating system is what actually provides the GUI with its specific design, layouts, and functionalities, ensuring the user experience is consistent and familiar.