Which technical combination is correct for painting soft clouds and a defined building in the same watercolour?

Correct answer: Wet-on-wet for clouds and wet-on-dry for the building

Watercolour technique is chosen according to the desired edge quality. Wet-on-wet lets diluted pigment spread softly into a damp surface, which suits rounded, hazy clouds. Wet-on-dry places paint on a dry surface, so the pigment remains more controlled and produces defined architectural edges. Very wet paper would blur the building, dry brush would not create soft clouds effectively, and the final option reverses the appropriate effects. Therefore, A is correct.