Chameleons contain crystals that reflect light and produce colour. Adjusting the spacing between these crystals, they can alter the wavelengths of light reflected, thus changing their skin colour. Based on the above information, we can infer that the change in colour by chameleons is a:

A. chemical change because change in colour takes place.
B. chemical change because wavelength of reflected light changes.
C. physical change because the space between crystals is adjusted.
D. physical change because light is reflected by crystals.