Which type of edge is more likely when wet colour is applied over wet colour?

Correct answer: A soft and diffused edge

The governing concept is the wet-on-wet painting method. Because the underlying surface is wet, the new colour moves into it and the boundary loses sharpness, producing a soft, diffused edge. Therefore, option D is correct. A hard, cut, or metallic edge requires different treatment and does not normally result from colour spreading across a wet surface.