Which sequence is more controlled for adding a dark shadow over a light watercolour wash?

Correct answer: Dry the light layer and apply a darker transparent layer

Watercolour is generally controlled from light to dark because transparent pigment cannot easily restore a light passage after it has been overwhelmed. Allowing the light wash to dry creates a stable base; a darker transparent glaze can then be placed selectively to form the shadow while preserving the underlying colour. Rubbing wet paint causes blooms or paper damage, black-first work reduces transparency, and rewetting the whole area spreads pigment unpredictably. Thus, A is correct.