If a flower-like mark forms after dropping dark colour on a damp watercolour surface what causes it?

Correct answer: Water and pigment spread in different directions and form irregular edges

The governing watercolour concept is a bloom, also called a backrun. When a damp area receives extra water or a wet drop, the liquid moves outward through the still-moist paint and pushes pigment toward an uneven boundary. This produces the flower-like edge described in the question, so option D is correct. The paper does not simply change colour, the brush does not harden, and instant drying would prevent spreading rather than cause it.