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

Engine parameters shall be corresponded to NOx Technical Files. This is required by （）

During the diesel engine running, the water level of F.W expansion tank should normally kept in the （） level of glass tube.

The Port State Control officer may witness a fire drill carried out by the crew assigned to these duties on the（）

When does auxiliary burner of incinerator put into operation? （）Ⅰ. start incinerator when it is coldⅡ. the sludge for dealing with is littleⅢ. the sludge for dealing with is largeⅣ. the water and impurity in sludge are too muchⅤ. the temperature in incinerator is lowⅥ. dealing with little solid rubbish

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

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.

“Insufficiency of manning or insufficiency of certification of seafarers” is an identification of a（）

Under MARPOL Code the ship to which it applies has to carry （）

Using a file without a handle may result in （）