Final answer:
Redwood is commonly used in cooling towers due to its moisture resistance and durability in wet conditions.
Step-by-step explanation:
The type of wood commonly used in cooling towers is Redwood(C). Redwood has been traditionally chosen for cooling towers because of its natural resistance to moisture, rot, and insects. It is capable of withstanding the humid and wet conditions prevalent inside a cooling tower. Other woods like cedar may also be used, but Redwood's longevity in wet environments makes it a preferred choice for this application.