Answer:
A set of headphones is an output device
Step-by-step explanation:
an output device is electronic hardware device that is used to showcase/produce the input been made into an electronic system usually a computer system. examples of such devices are speakers, monitors printers and scanners.
A set of headphones is an output device because it reproduces the music been downloaded ( input ) into the electronic/computer system been used for the downloads. while an input device is the means through which the music was downloaded into the computer system that the headphone will be connected to reproduce the music.