单项选择题
A.the main engines
B.the auxiliary engines
C.the emergency generator engine
D.the auxiliary engines and the main engine(s)
单项选择题 A full-flow 50μm filter is installed ,（） so the injection system components on the main engine are safeguarded.
单项选择题 The fuel from the bunker tanks must be treated by before entering the service tanks（）, from where the fuel enters（）
单项选择题 When the heavy fuel oil is heated to achieve the viscosity of 10-15 cst, may occur.To avoid this, a system is used in most occasions（）