If a small round poster-colour dot becomes oval which technical cause is most likely?

Correct answer: The brush was dragged instead of lifted vertically

The governing technique is the press-and-lift brush stroke. A round dot is formed when the loaded brush touches the surface and is lifted vertically without sideways movement. If it is dragged, wet paint stretches in the direction of motion and the circular mark becomes oval. Therefore option C is the most direct cause. Excess water may cause spreading, and uneven bristles may roughen an edge, but neither specifically explains directional elongation as well.