Which action is suitable for creating a soft transition between two colours while acrylic paint is wet?

Correct answer: Gradually blending both colours along their shared boundary

A soft transition, or gradient, is created by wet blending: the edges of two still-wet colours are gently worked together along their shared boundary. This produces a gradual change rather than a sharp line, so option A is correct. Scraping a dry layer, spraying varnish, or using only a dry brush does not provide the required wet colour transition.