Cast iron carrier rings, （） machined grooves, are provided for all the pistons.

A.to prevent the fuel system from becoming air-hound
B.to prevent the fuel system becoming clogged with dirty particles
C.both of the above
D.to prevent the lubricating oil from leaking out of the filter element

A.diameters of journals
B.deflections of crankwebs
C.diameters of crankpins
D.none of the above

A.the cylinder cover is cracked
B.the injector holes is clogged
C.the cams are not properly set
D.fuel pump is leaking