How may a sphere appear if the core-shadow boundary is too hard?

Correct answer: Angular or cut

The governing concept is a gradual value transition on a curved surface. A sphere normally shifts from light through halftone and midtone toward core shadow without a sharp, graphic break. If the core-shadow boundary is excessively hard, the eye reads it as a sudden change of plane rather than a continuous curve, so the sphere may look angular or cut. Therefore C is correct; hardness does not make it transparent, distant, or automatically shinier.