单项选择题
A.the system is fully charged
B.there is air leaking in from the condenser
C.ice crystals are forming in the refrigerant
D.the system contains less than a full charge of refrigerant
单项选择题 Which of the filter/strainer units listed permits you to clean the element while leaving the system on the line?（）
单项选择题 A sight glass is installed in the liquid line to indicate the condition of the refrigerant charge and may also indicate the （）.
单项选择题 If one hydraulic pump of an electro-hydraulic steering unit falls, the vessels steering can be initially and best maintained by using the （）.