Final answer:
A 4" supply line is jacketed with synthetic rubber impregnated with synthetic fibers, providing a flexible and durable protective covering.
Step-by-step explanation:
A 4" supply line is jacketed with synthetic rubber impregnated with synthetic fibers.
The term 'jacketed' refers to the protective covering or outer layer that is wrapped around the supply line.
In this case, the jacket is made of synthetic rubber, which is a flexible and durable material. The synthetic fibers further reinforce the jacket, making it stronger.