单项选择题
A.It is lower than the ignition temperature
B.It is the temperature at which a substance will spontaneously ignite
C.It is the temperature at which a substance, when ignited, will continue to bum
D.It is the temperature at which the released vapors will fall within the explosive range
单项选择题 Sludge may form in the crankcase of an air conditioning compressor as a result of （）.
单项选择题 Which of the following centrifugal pump components converts the liquid kinetic energy of velocity to the potential energy of pressure?（）
单项选择题 Excessive circulation of the lubricating oil with the refrigerant in a refrigeration system will cause （）.