How does pigment concentration affect spreading in wet-on-wet technique?

Correct answer: A more watery mixture generally spreads farther

The governing concept is capillary movement and flow on a moist watercolour surface. A watery mixture has lower pigment concentration and more mobile liquid, so it can travel farther through the damp paper and soften over a wider area. A thicker mixture usually deposits more pigment near the starting point, although it can still spread somewhat. Direction is not restricted to upward movement, and concentrations do not spread equally; therefore D is correct.