When the vessels steering wheel on the navigation bridge is turned, the difference existing between the position of the wheel and that of the rudder is known as （）.

A.Dehydrators must be used continuously in a refrigeration system
B.A 25 ton refrigeration system has the same cooling effect as melting 25 tons of ice in 24 hours
C.A thermostatic expansion valve is used to control refrigerated space temperature
D.The liquid receiver functions to collect and remove non- condensable gases

A.Hydraulic
B.Mechanical
C.Pneumatic
D.Electrical