单项选择题
A.spraying directly on the base of the fire
B.flowing the foam down a vertical surface
C.sweeping the fire before you with the foam
D.spraying directly on the surface of the fire
单项选择题 During the inspection, the starting air valves should be closed （）the engine from turning.
单项选择题 The viscosity regulator controls the fuel oil temperature （）provide oil at the correct viscosity for combustion.
单项选择题 To avoid scavenge fires occurring the engine timing and equipment maintenance （）.