The correct answer is D. Microsoft Windows.
An operating system (OS) is a system software that manages computer hardware and software resources and provides common services for computer programs. Operating systems are found on many devices that contain a computer â from cellular phones and video game consoles to web servers and supercomputers.
Microsoft Windows is a group of several proprietary graphical operating system families, all of which are developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. Active Windows families include Windows NT and Windows IoT; these may encompass subfamilies, e.g. Windows Server or Windows Embedded Compact (Windows CE). Defunct Windows families include Windows 9x, Windows Mobile and Windows Phone.
Microsoft Windows dominates the personal computer market with a market share of over 80%, and is the most widely used desktop OS in the world.