单项选择题
A.Control of evaporation
B.A separate means to prevent feed-water contamination
C.Power circulating pump
D.Super-heater
单项选择题 Prior to lighting off a cold automatically fired auxiliary boiler, yon should （）.
单项选择题 After a normal, or safety shutdown, automatic combustion control systems for an auxiliary boiler are designed to prevent the immediate re-firing of a burner in order for the （）.
单项选择题 （） will be used to blow away soot and the combustion products from the tube surfaces.