单项选择题
A.to increase
B.to speed up
C.to prevent
D.to reduce
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 （）.
单项选择题 Combustion knock can occur in the cylinders of a diesel engine under any condition permitting （）.