单项选择题 In general, the oil mist defectors include a base plate with air blast pumpThe function of air blast pump is to （）crankcase.

单项选择题 In general, the oil mist detectors include a built-in heating unit and a compact plug for electrical connectionThe function of heating unit is to （）

单项选择题 （）continuously extract the crankcase atmosphere, via a pipe system, and move it past a sensitive and accurate opacity measuring track.