How can the flat cut surface of a fruit be distinguished from its rounded outer surface?

Correct answer: By using less gradation on the flat area and more on the rounded surface

The governing concept is how light changes across planes and curves. A flat cut plane usually holds a more even value, while a rounded outer surface shows gradual transitions from light to middle tone to shadow. Option C is correct because it describes this difference. Identical values hide the planes, erasing a contour does not model them, and blackening the fruit removes useful value information.