Letter c. projecting a computer image on to a screen.
Explanation:
Video projectors are of frequent use in classrooms, conference rooms, and theaters, especially movie theaters. They are electronic devices capable of taking audio/visual inputs and then projecting them (output) as a video onto a flat surface. That surface can be a white screen or even a wall, for that matter. The output video can be much larger than the original images.
This excerpt shows that while Martin Luther King Jr and Gandhi are two of the most widely known civil protesters they are not the first nor the most important.
