When you look through a sheer curtain at a distant street lamp, you see a pattern of colored spots of light. This occurs by
a. polarization of light in scattering and partial absorption by the threads
b. interference of light waves that pass through the threads with light waves that pass through the openings between the threads
c. refraction of light waves differentially in the cylindrical threads
d. diffraction of light waves passing through the two dimensional pattern of openings between the threads