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

Which one is NOT the ‘clear grounds’ for a more detailed inspection?（）

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

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?（）

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

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

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

Using a file without a handle may result in （）