单项选择题
A.prevent an internal explosion in the pump when it is overheated
B.enable a visual inspection of the pump while it is running
C.insure a proper alignment of the pump coupling to the driver
D.accommodate for friction between the impeller and the easing
单项选择题 The lowest temperature required to cause self-sustained combustion of a substance independent of any outside source of ignition is called （）.
单项选择题 If a refrigeration compressor will not start, the reason may be （）.
单项选择题 Which of the following statements describes the relationship between flash point and ignition temperature?（）