单项选择题
A.clogged filters
B.poor combustion
C.overloading of the diesel
D.shock of fuel lines
单项选择题 Diesel oil may be used to cool （） of a diesel engine.
单项选择题 Diesel engines are started by supplying （） into the cylinders in the appropriate sequence for the required direction.
单项选择题 Diesel engines are started by supplying （） into the cylinders in the appropriate sequence for the required direction.