单项选择题
A.replace all bearings regardless of length of service
B.apply a heavy coat of oil to all mating surfaces
C.clean any corroded surfaces and file all burrs smooth
D.coat all parts with alemite grease
单项选择题 Ammeters and voltmeters used in sinusoidal AC power systems indicate which of the following values of the waveforms measured?（）
单项选择题 Fuses placed in series with a thermal trip-type circuit breaker are used for （）.
单项选择题 The main difference between a motor control circuit containing low voltage protection and low voltage release is that the latter contains （）.