单项选择题
When start a screw pump, the by pass valve should be （）.
A.closed B.opened fully C.cracked open D.partly open
单项选择题 A centrifugal pump can’t supply water after startingYou should check （）.
单项选择题 Open the （）of inter cooler before starting an air compressor.
单项选择题 Open the （）before starting an air compressor.
