Why is it necessary to distinguish core shadow from reflected light?

Core shadow is the dark turn of form, reflected light is bounced light in shadow side

The governing concept is the internal organisation of the shadow side. Core shadow is the darker band where the surface turns away from the main light and receives little direct illumination. Reflected light is weaker light bounced from a nearby floor, wall, or object into part of that shadow side. It usually lifts the lower or outer edge without becoming brighter than the light-facing side. Confusing the two can flatten the form, reverse the light logic, or make the shadow side unnaturally bright. Option A is correct because it identifies both functions accurately. Option B ignores their different causes, C misidentifies reflected light as the darkest area, and D wrongly denies the role of illumination.

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