The device, which is installed in the compressor suction line to prevent liquid from entering the compressor when hot gas defrosting, is called a（）

单项选择题The humidity of the atmosphere can be determined by the use of the（）

A.anemometer
B.potentiometer
C.manometer
D.psychrometer

单项选择题In a centrifugal Freon refrigeration system, the overall capacity of the system is increased by（）

A.opening more bypass lines
B.opening additional expansion valves
C.adding refrigerant
D.speeding up the machine

单项选择题The main distribution duct in an air conditioning system which contains the cooling coils and filters is called the（）

A.manifold
B.condenser
C.chamber
D.plenum

单项选择题If a compressor runs continuously, the cause might be a（）

A.defective thermal bulb
B.clogged scale trap
C.stuck high-pressure switch
D.stuck low-pressure switch

单项选择题Which of the following would not cause high suction pressure?（）

A.insufficient refrigeration
B.leaky suction valves
C.expansion valve stuck open
D.suction valve not adjusted properly