How can natural variation be introduced while maintaining unity among several flower petals?

Correct answer: By slightly varying angle and pressure in similar strokes

Unity comes from repeating a related basic stroke, while natural variety comes from making small controlled changes within that pattern. Slightly altering the angle and pressure changes each petal’s curve, width, or emphasis without destroying the visual relationship, so option D is correct. Different tools for every petal would reduce unity, and erasing or drawing only one petal cannot create the required group.