The correct answer is C) reduce the feed water flow to the boiler. When the water level in a steaming boiler rises to within 2 inches of the top of the gage glass, it indicates that the feed water flow to the boiler is excessive. Reducing the feed water flow will help lower the water level and prevent it from going too high, which could lead to water carryover into the steam system or potentially even a boiler explosion. The other options, such as securing the fires and opening the blow valve (A) or opening the surface blow line (B), are not the immediate actions required in this situation. Securing the feed water flow (D) is also not the correct response, as the goal is to reduce the flow, not stop it completely.