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单项选择题
A.rotary compressors
B.reciprocating compressors
C.centrifugal compressors
D.screw compressors
单项选择题
A.starting diesel engines
B.pneumatic control systems
C.pneumatic tools
D.supercharging air
单项选择题
A.globe valves
B.butterfly valves
C.gate valves
D.reducing valves
单项选择题
A.a sewage treatment plant
B.the extended aeration process
C.the liquor
D.the bubbling air
单项选择题
A.in boiler drums
B.in refrigerating plants
C.in starting air pipes
D.in air coolers