Large crosshead type engine generally has two lubrication systems, a function performed only by crankcase oil system is（）

单项选择题Large crosshead type engine generally has two lubrication systems, a function performed only by cylinder oil system is（）

A.lubricating
B.cooling
C.sealing
D.cleaning

单项选择题In some diesel engine designs,（）the injection of cylinder oil is timed to impinge when the piston and only impinge on（）

A.is coming upward；cylinder ring belt
B.is going downward；piston ring belt
C.is coming upward；piston ring belt
D.is going downward；cylinder ring belt

单项选择题（）diesel engines generally have two systems of lubrication:（）a total loss system feeding and a circulating system lubricating the running gear and cooling the pistons.

A.Large crosshead type；crossheads
B.High speed；the cylinders
C.Large crosshead type；the cylinders
D.Four-stroke；pistons and cylinders

单项选择题The following options are all the functions of lubricating oil except（）

A.removing heat and deposits
B.neutralizing acidic products
C.lubricating
D.improving combustion efficiency

单项选择题The air distributor is conventionally driven by（） and distributes into each cylinder by（） certain sequence.

A.camshaft；fresh air
B.camshaft；starting air
C.electronic motor which is controlled by a computer；fresh air
D.electronic motor which is controlled by a computer；starting air