Which type of instrument is categorized as an idiophone?

An idiophone is a type of musical instrument that produces sound primarily by the vibration of the instrument itself, without the use of strings, membranes, or air. The defining characteristic of idiophones is that the sound is generated from the material of the instrument when it is struck, shaken, or scraped. Common examples include bells, cymbals, marimbas, and xylophones, where the body of the instrument itself vibrates to create sound.

The option that correctly identifies idiophones states that they produce sound by being struck. This detail highlights the fundamental mechanism of how idiophones operate, emphasizing their unique nature among other families of instruments. The other options describe other types of instruments: those that require air (aerophones), those that use membranes (membranophones), and those that are played with bows (chordophones). Each of these families has distinct methods of sound production that do not apply to idiophones.