What does edge hierarchy mean in form drawing?

Showing depth and focus by keeping some edges sharp and some soft

The governing concept is edge hierarchy, the deliberate variation of edge clarity according to form, light, distance, and visual importance. A sharp or hard edge can attract attention and clarify a strong boundary, while a soft or lost edge can suggest a turning surface, reduced contrast, atmosphere, or lesser focus. Option A is correct because this controlled variation helps the viewer read depth and decide where to look first. Keeping every edge equally sharp can make the drawing mechanical or cut out; removing all edges destroys useful structure; and saying edges have no relation to form ignores their role in describing turning surfaces. Edge hierarchy does not mean careless fading: each edge should support the object’s volume and the intended focal point.

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