To avoid scavenge fires （） the engine timing and equipment maintenance should be correctly carried out.

Those generally used additives for cooling water are ei...

单项选择题Those generally used additives for cooling water are either anti-corrosion oils or inorganic（）.

This used piston had been tested and approved as a spar...

单项选择题This used piston had been tested and approved as a spare part by the （） during last annual repair.

They understand the （） of automatic sludge discharging ...

单项选择题They understand the （） of automatic sludge discharging of the purifierBut they are not good in practice.