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

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

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

Which of the listed governor characteristics will greatly affect the load sharing relationship between paralleled diesel generators?（）

As soon as a diesel engine has started, which of the listed engine operating parameters should be checked FIRST?（）

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

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

（） is not installed on the main switchboar.

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

To shut down a diesel engine after it exceeds the set maximum speed，which type of device listed should be used?（）