The output volume of a positive fixed displacement pump can be changed only by （）.

An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.

A grease gun is generally used to lubricate a （）.

Which of the listed pumps is NOT a positive displacement pump?（）

If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.

Who is responsible for ensuring that someone is assigned to close the watertight doors in an emergency?（）

If the thermal bulb of an expansion valve is incorrectly placed at the center of the coil instead of the end, it will （）.

Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.

When the steering gear is in operation, you should （）.

An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.