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

Cold weather starting of a diesel engine may be made easier by（）

Diesel engine air start system check valves are opened by （）

By comparing the exhaust gas temperature of each cylinder, the operator can determine if the load is balanced throughout the engine. The device most commonly used is a（）

To proceed to the assistance of a ship in distress is（）

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

（） is not installed on the main switchboar.

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

Flame failure in an automatically fired auxiliary boiler can from a/an （）

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