Which correction technique is most suitable for creating a thin ray of light from dried colour?

Correct answer: Lifting colour with a clean damp brush

The governing concept is controlled lifting in watercolour correction. A clean damp brush can soften or remove pigment from a narrow selected path, exposing a lighter paper tone and producing a thin ray of light. B is therefore correct, especially when the pigment has some liftability. Rewetting the whole area loses control, black paint darkens rather than lightens it, and salt creates a texture effect rather than a precise beam.