单项选择题
A.the low inertia
B.the high inertia
C.the low velocity
D.the high velocity
单项选择题 A （） in the air delivery line near to each compressor is essential.
单项选择题 Adequate attention must be given to the water cooling system of the air compressors, for （） can cause condensation on the cylinder walls.
单项选择题 Bad valves operation of the reciprocating air compressors can be detected by observation of （）.