What is the benefit of making lines with fast and slow hand movement in line practice?

It helps understand differences in line energy and control

Practising lines at different hand speeds helps the learner observe how movement affects line quality. A quick movement may produce a lighter, more energetic, spontaneous, or sweeping mark, whereas a slower movement usually allows greater control, steadiness, pressure adjustment, and attention to accuracy. The exercise therefore develops awareness of both line energy and motor control, making it useful for expressive drawing as well as careful observation. Option A is correct because it identifies the actual learning benefit. Options B, C, and D describe effects that do not follow from changing hand speed: paper colour does not automatically change, a drawing still requires visible marks, and the lines do not become invisible. The governing concept is that physical movement influences the character of a drawn line.

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