Match each of the following components to its category of Input or Output.
3D Printer - Output Device
Digital Camera - Input Device
Headphones - Output Device
Touch screen - Input Device
B and D are input devices, A and C are output devices
Remember this is from the perspective of a computer, so a camera connected to a computer is generally there to upload photos and videos from it, or perhaps to use it as a video camera input for streaming.
If your headphones also have a microphone attached then they could also be used for input, but they are always able to provide (sound) output.
Of course, a touch screen is used for both input and output, but the touch aspect is for input.