Which of the materials listed is used as the dynamic seal material on mechanical seals installed on most centrifugal pumps used in water service?

Correct Answer: Option B — Carbon.

Carbon is the industry-standard material for the rotating or stationary face of a mechanical seal. Its self-lubricating properties, low coefficient of friction, and excellent thermal conductivity make it ideal for maintaining a dynamic seal against a harder mating surface, such as ceramic or tungsten carbide, in water service applications.