单项选择题
A.remove suspended and precipitated solids from the boiler water
B.completely drain the boiler in an emergency situation
C.prevent hardened scale deposits in the water drum
D.remove floating impurities from the oily water surface
单项选择题 A three-way thermostatic control valve regulates the diesel engine cooling water temperature by passing a portion of the water （）.
单项选择题 The concentration of total dissolved solids in the water of an auxiliary boiler can increase as a result of （）.
单项选择题 The water in an auxiliary boiler should be tested for chloride content to determine （）.