Which method is useful for creating a soft edge in watercolour?

Correct answer: Apply paint on wet paper

The governing technique is wet-on-wet painting. Moisture already present in the paper allows the fresh watercolour to travel gradually beyond the stroke, producing a blurred and soft edge. Thus, option A is correct. Thick paint on dry paper usually creates a sharper boundary, cutting the paper does not create a painted edge, and a dry brush gives a broken or textured mark rather than a soft one. The sheet should be damp, not covered with standing water.