Most marine biological sewage treatment plants consist of all the following statements except （）.

A、aeration tanks

B、settling tanks

C、disinfection agent

D、anaerobic bacteria

The thermal expansion valve responds to the（）

A、amount of superheat in the vapor leaving the coil

B、amount of superheat in the liquid

C、temperature in the evaporator coils

D、pressure in the evaporator coils

When oily water separator is operating, which measure （） is wrong.

A、pay attention to operating parameters

B、renew and clean separating units in time

C、check oil level in separator to prevent overload

D、check separating effect, if it is bad, flush with large capacity water pump

Most anchor handling equipment incorporates （） for mooring purposes.

A、cable lifters

B、spur wheels

C、bollard

D、warpends

The load between two steam-driven alternators operating in parallel may be adjusted by varying （）

A、the speed of the alternators

B、the field strength of the machines

C、the power factor of the alternators

D、steam supply to the prime movers

Which of the following problems will occur if the internal drain at either end of a hydraulic, two-way, spool-type directional control valve cylinder were to become plugged?（）

A、The reservoir would become vapor bound

B、The valve would be placed in hydraulic lock

C、The spring loaded relief ports would open

D、The buffering chambers would be unable to function