The middle area became muddy while creating a warm-to-cool colour transition. What is the most likely cause?

Correct answer: Incompatible colours were overmixed by repeated rubbing

The governing concept is controlled colour transition. Warm and cool colours can lose clarity when incompatible pigments are repeatedly rubbed and overmixed; this produces a dull or muddy middle area. Option B is therefore the most likely cause. Dry paper, a small brush, or applying the lighter colour first may affect handling, but none automatically creates muddiness. A cleaner transition requires limited mixing and deliberate intermediate tones.