The delivery rate of a variable stroke axial piston hydraulic pump is controlled by varying the position of the （）.

A.Liquids with different viscosities will always have the same specific gravity
B.Liquids with different viscosities will never have the same specific gravity
C.Viscosity and specific gravity are directly proportional
D.Viscosity and specific gravity are not related in that one does not define or limit the other

A.stored at temperatures below 60 degrees Fahrenheit
B.charged into a system having copper fittings
C.allowed to mix with compressor oil
D.exposed to an open flame or hot surface

A.acid formation
B.sludge formation
C.ice in the expansion valve
D.All of the above