While engine is in operation the piston moves up and down, thus causing the rotation of the （）.

A.leaky injector
B.water in the gas
C.too heavy oil
D.water in the oil

A.bearing knocks
B.dropping of pressure of LO
C.noises
D.all the above

A.to remove heat from oil cooled pistons
B.to wash away wear detritus
C.to neutralize acidic products
D.all of the above