Final answer:
The device that raises the temperature to a maximum of 210°F is a steam boiler, as it heats water to produce steam, which typically involves temperatures above water's boiling point at atmospheric pressure.
Step-by-step explanation:
When considering a device that raises the temperature to a maximum of 210°F, we should identify the device by its purpose and the temperature it can reach. A water heater typically heats water to temperatures comfortable for domestic use and does not usually reach 210°F. On the other hand, a steam boiler is designed to generate steam by heating water beyond its boiling point under atmospheric pressure, which is 100°C (212°F). Thus, a steam boiler is capable of reaching and exceeding the specified temperature of 210°F. An expansion tank is a component of a heating system that allows for the expansion of water and does not itself heat water. A gas heater is a more general term and could refer to any appliance that uses gas as a heating source, including both water heaters and boilers.
Given the information provided, the correct answer to the temperature reaching a maximum of 210°F is a steam boiler (B).