Final answer:
A tri-indicator is typically found on a steam boiler and monitors pressure, temperature, and water level to ensure safe operation.option b is correct
Step-by-step explanation:
A tri-indicator is typically found on a steam boiler. This device is used to indicate three important parameters that are crucial for the boiler's operation: pressure, temperature, and water level. In the context of a steam boiler, the tri-indicator allows for the monitoring of the system to ensure it's running within safe operational limits.
A hot water boiler and special boilers may use different types of gauges or indicators that are specific to their design and operation. For instance, hot water boilers may not require the same level of pressure monitoring as steam boilers. The distinction is important because steam boilers operate at higher pressures and thus have different safety requirements compared to hot water heating systems.