ANS:C - Feed water pump

Among the options provided, the "Feed water pump" is a boiler accessory, not a boiler mounting. Boiler mountings are those parts that are mounted on the boiler itself and are essential for its safe and efficient operation. On the other hand, boiler accessories are optional components that aid in the overall functioning of the boiler system. The feed water pump is an accessory as it assists in supplying water to the boiler. The other options listed (Blow off cock, Feed check valve, Stop valve) are boiler mountings.