What Observational Setup Is Required to Observe Backlit Rings

Multiple Choice

What observational setup is required to observe backlit rings?

A) The light source doing the backlighting has to have wavelengths much longer than the size of the ring particles.
B) The light source doing the backlighting has to have wavelengths comparable to the size of the ring particles.
C) The light source doing the backlighting has to have wavelengths much shorter than the size of the ring particles.
D) The light source doing the backlighting must be a blackbody source peaking in the visible part of the spectrum.
E) The light source doing the backlighting must be very distant