Which example shows one device performing both input and output roles?

Correct answer: Touchscreen

The governing concept is the distinction between input and output devices. A touchscreen displays text, images, and controls, so it performs an output function; it also detects a user’s touch and sends that information to the computer, so it performs an input function. Thus option C is correct. A basic speaker produces sound, a keyboard only enters keystrokes, and a printer produces printed output, so those choices do not normally perform both roles.