Which correction is best if a highlight is accidentally painted while still wet?

Correct answer: Gently lift the colour with a clean, damp brush

The relevant watercolour correction method is lifting. When the paint is still wet, a clean, damp brush can absorb and remove some pigment from the highlight area. The brush should be rinsed and lightly blotted between strokes so that it lifts colour instead of spreading it. A darker colour only hides the highlight, scratching can tear or roughen the paper, and oil is unsuitable for watercolour paper. Thus option B gives the safest and most effective correction.