The correct answer is: C. 1988
The X Window System (X11) is a network protocol and graphical user interface (GUI) toolkit for creating graphical user interfaces. It was created by Bob Scheifler and Jim Gettys at MIT in the mid-1980s, and released in 1988. X11 is a client-server protocol, with the client being the application that displays the GUI, and the server being the program that manages the display hardware. X11 is a cross-platform protocol, meaning that it can be used on a variety of different operating systems, including Linux, macOS, and Windows.
Option A: 1984 is incorrect because the X Window System was not released until 1988.
Option B: 1989 is incorrect because the X Window System was released in 1988.
Option C: 1988 is the correct answer because the X Window System was released in 1988.
Option D: 1990 is incorrect because the X Window System was released in 1988.
Option E: None of the above is incorrect because the X Window System was released in 1988.