The main purpose of port State control is not to（）

Using a file without a handle may result in （）

（）are used to digest the sewage to produce innocuous sludge in a biological sewage treatment plant.

If two A.C.generators are to be operated in parallel, the load is distributed evenly by（）

If separating effect is not good, which measure should be taken （）

The additional mark （）in the Classification Certificate for Machinery means propulsion apparatus is remotely controlled on the navigating bridge control station, and engine assembly control station is unmanned periodically.

（） is not installed on the main switchboar.

A purge recovery system is used in a centrifugal air conditioning or refrigeration system to （）

For a given exhaust gas boiler, what is the quantity of its evaporation mainly determined?（）

Which of the diesel engine components listed increase air density and helps to improve engine operating efficiency?（）