单项选择题
A.check and regulate the water level
B.close the air cock once fires are lit
C.blowdown the gage glass
D.crack the steam stop to assure protective steam flow
单项选择题 Which of the following statements describes the function of an expansion tank in a diesel engine cooling system?（）
单项选择题 To minimize corrosion, fuel oil strainer disks, spacers and scraper blades are made of （）.
单项选择题 The expansion tank for a diesel engine closed cooling system is designed to maintain a constant head on the system and （）.