Which exercise is most useful for learning watercolour technique?

Correct answer: Practise flat wash, graded wash and wet-on-wet

The governing concept is technique practice: watercolour depends on controlling pigment, water and brush movement. Flat wash develops an even layer, graded wash develops a smooth change from dark to light, and wet-on-wet teaches controlled spreading on damp paper. Therefore, option B directly builds practical watercolour skills; writing names, folding paper and keeping a dirty brush do not develop painting control.