Which brush is useful for painting small round flowers with acrylic colour?

Correct answer: Small round brush

Brush selection is governed by the relationship between brush shape and the mark required. A small round brush has a pointed tip and controlled belly, allowing the artist to place compact curved strokes for small petals and circular forms. Therefore option A is correct. A broad flat brush is better for large areas, a wire brush creates rough effects, and a brush without bristles cannot carry paint properly.