Answer:
projector
Step-by-step explanation:
The output device that would be used would be a projector. From the available options, this is the only option capable of showing a movie to the class. A projector "projects" (in other words sends an image) the movie that was inputted into the machine onto a screen. This allows a video image to be shown on the screen which the entire class can see. Speakers only output audio, 3D printers output physical objects, and a braille embosser only outputs braille onto paper.