What happens if the value difference between two adjacent planes is too small?

Correct answer: The plane separation will become unclear

The governing concept is value contrast between planes. Adjacent planes need a sufficient light-dark difference for the viewer to read their separate directions and boundaries. If their values are nearly equal, the contrast is weak, so the plane separation becomes unclear; option B is correct. A small value difference does not lengthen a cast shadow or automatically create shine, and it generally reduces rather than improves clarity.