Why are different pencil grades used progressively?

Correct answer: To control a wide tonal range

The governing concept is that pencil grades vary in hardness and graphite softness, so they produce different marks and values. Harder grades are useful for lighter, finer lines, while softer grades create darker and richer tones. Using them progressively gives better control across a wide tonal range, making option A correct. Pencil grades do not change an object's size, remove a cast shadow, or alter the actual colour of the paper. Layering grades carefully also improves smooth transitions.