For what purpose can a sudden increase in line thickness be used?

To immediately emphasise a particular part of the picture

The governing concept is line weight and visual emphasis. A sudden change from a thin stroke to a thick stroke creates contrast, and the eye is naturally drawn toward that stronger mark. Artists may use this change to indicate a foreground edge, a shadowed boundary, an important contour, or a focal detail. Option A is correct because increased thickness gives that area greater visual force and priority. Option B is incorrect: equal importance would require more consistent treatment, not a sudden contrast. Option C is incorrect because thickness can strengthen direction rather than erase it. Option D is incorrect because heavy lines generally attract attention instead of hiding an object. Line weight should be controlled so emphasis supports the composition.

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