The correct answer is: D. All of the above
The SKETCHPAD system was a computer-aided design system developed at MIT in the 1960s. It was one of the first systems to use a graphical user interface, and it is considered to be a forerunner of modern computer graphics.
The SKETCHPAD system consisted of an cathode-ray oscilloscope driven by a Lincoln Tx2 computer. The oscilloscope was used to display graphical information on the screen, and the computer was used to control the display.
The SKETCHPAD system was used for interactive graphics. This means that the user could interact with the graphical information on the screen by using a mouse or other input device.
The SKETCHPAD system was expensive because it was sophisticated and made demands on the power and resources of the computer. It was one of the first systems to use a graphical user interface, and it required a powerful computer to run.
The SKETCHPAD system was an important development in the history of computer graphics. It was one of the first systems to use a graphical user interface, and it is considered to be a forerunner of modern computer graphics.