How can line explain both surface and boundary of an object differently?

Outline shows boundary and inner lines show surface texture

The governing concept is the functional difference between contour and interior descriptive lines. An outline or contour marks the outer boundary, separating the object from the surrounding space and defining its visible shape. Interior lines can describe folds, grain, wrinkles, ridges, fur, or other surface qualities; their direction and spacing may also suggest how the surface turns. Option A is correct because it assigns these two related but different jobs accurately. Option B reduces every line to an outside boundary and ignores texture. Option C is false because surfaces are not always understandable without marks. Option D ignores the descriptive and tactile information carried by interior lines. Good drawing uses line placement selectively so that boundary and surface information remain clear rather than competing.

This is a Class 9 Art Education question. Chapter: Elements of Art. Topic: Line.