How can lines show facial expressions?

By changing the direction of the lines of the eyebrows, eyes, and mouth

The governing concept is expressive line in portrait drawing. Small changes in the angle, curve, thickness, and position of facial lines can communicate a person’s mood. Raised eyebrows and an open, curved mouth may suggest surprise; a downturned mouth or tense brows may suggest sadness, worry, or anger. Thus option A is correct because the important visual information is carried by the lines defining the eyebrows, eyes, and mouth. Changing paper size changes the support, not the expression. Background lines may add setting but cannot by themselves define the face, and adding more paint to a brush changes material coverage rather than the meaning of the facial features. Observing these features together gives the clearest reading.

This is a Class 9 Art Education question. Chapter: Elements of Art. Topic: Line.