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 C — Carbon.

Carbon is the industry standard for the stationary or rotating face of a mechanical seal in water service. Its self-lubricating properties, low coefficient of friction, and ability to withstand thermal shock make it ideal for maintaining a tight seal against a harder mating surface like ceramic or tungsten carbide.