Final answer:
Brushes with natural bristles that have tiny overlapping layers or scales, which clean and add luster to the hair, can be synthetic, natural, or plastic bristles. Therefore, the correct option is b.
Step-by-step explanation:
Synthetic bristles are made from man-made materials and are often used in brushes for their durability and affordability. Natural bristles are typically made from animal hair, such as boar or horsehair, and are preferred for their ability to distribute oils from the scalp to the hair. Plastic bristles can also be used in brushes, but they do not have the same ability to clean and add luster to the hair as natural bristles.