When a compact disc is illuminated by small source of white light, coloured bands are observed.  This is due to
a)	Dispersion	b)	Diffraction	c)	Interference	d)	Reflection

(b)

The data which represents the music is stored on the compact disc in the form of very small pits arranged in a tightly wound spiral track in silvery surface.  The distance between two neighbouring track is 1.6 micrometre.  Which is only several times the wavelength of visible light, this small spacing is responsible for the wonderful colours reflected by a CD which works as a diffraction grating.  Hence, diffraction is responsible for coloured bands.