In which condition is it necessary to keep a shape boundary clear?

When a sign or symbol must be easily recognized

The governing concept is clarity of shape in visual communication. A clear boundary separates the figure from its background and allows the viewer to identify its outline quickly, even from a distance or for a short viewing time. Option A is correct because a sign or symbol must communicate its meaning immediately and consistently; a sharp, readable contour supports recognition. Option B and option C describe mist and smoke, whose soft edges can suggest diffusion and movement. Option D directly asks for an unclear shape, so it contradicts the requirement of a clear boundary. The choice of edge is therefore functional as well as decorative: instructional and public symbols usually need strong contours, while atmospheric subjects may use blurred ones.

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