a). Dholak is a type of musical instrument. These two sides have a thin stretched membrane. When its head is beaten by anything then it vibrates and produces the sound.
b). Sitar is a type of musical instrument. In this the streched strings are presented. When this is touched by anything it vibrates and produces the sound.
c). Flute is a type of musical instrument. In flute there are some holes on the surface and an air column inside the flute when it vibrates produces the sound.
Final Answer –
a). Thin stretched membrane
b). Stretched string
c). Air column