单项选择题
Some refrigeration systems have chemical moisture indicators installed in conjunction with the sight glass in the liquid lineIf excess moisture is present in the system, the indicator will （）
A.activate the driers B.change color C.secure the compressor D.add a predetermined amount of liquid drier
单项选择题 In the navigation, cause the shafting over load most easily（）
单项选择题 The oil index of main engine should be controlled to prevent it from in heavy weather（）
单项选择题 A dry-type spark arrestor removes sparks from a diesel engine exhaust by（）
