单项选择题
The cooling water of the diesel engine should be treated, because it has（）
A.alkale scence B.acidity C.salinity D.impurity
单项选择题 When received the order "finished with engine" which of the following operations is wrong?（）
单项选择题 When the diesel is stopped, which of the following items is wrong?（）
单项选择题 After finished the engine, which of valves cannot be shut off by the duty engineer?（）
