单项选择题
A.molecular fluid vibration
B.energy losses
C.wide pressure variations
D.mechanical damage to control valves
单项选择题 Which of the conditions listed represents the greatest effect of excess frost accumulation on the evaporator coils?（）
单项选择题 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 （）.
单项选择题 Which of the listed statements is correct concerning refrigeration systems?（）