Final answer:
Nylon bristles are the best choice for new cleaning brushes due to their durability and resistance to moisture, making them ideal for commercial kitchen use.
Step-by-step explanation:
The best choice of bristle for new cleaning brushes that are long-lasting and do not absorb moisture would be nylon bristles. Nylon is a synthetic material that is well-known for its durability and resistance to moisture absorption. In contrast, horsehair and boar bristles are natural fibers that can absorb moisture and are not as durable as synthetic fibers. Plastic bristles may also be durable, but they can vary widely in terms of quality and moisture resistance. Therefore, nylon bristles are the superior choice for the foodservice manager's needs, offering a combination of longevity and resistance to moisture that is ideal for cleaning brushes in a restaurant or commercial kitchen environment.