Why is a small change in eyebrow and mouth lines important in an expressive face?

It can completely change the facial expression

The governing concept is facial expression through economical line placement. Eyebrows and the mouth are highly expressive features because their angle, curve, height, and tension communicate emotional states. A slight upward or downward change can suggest happiness, sadness, anger, worry, surprise, or doubt, even when the rest of the face remains almost unchanged. Therefore option A is correct: a small alteration in these lines can substantially change the message read by the viewer. Option B concerns paper rather than expression. Option C is impossible in this context, and D confuses the function of drawing lines with the behaviour of colour. Careful observation and controlled line variation are essential in portrait drawing.

This is a Class 9 Art Education question. Chapter: Portrait Drawing. Topic: Facial Expressions.